# Python API¶

This page provides detailed documentation for the tskit Python API.

## Trees and tree sequences¶

The TreeSequence class represents a sequence of correlated evolutionary trees along a genome. The Tree class represents a single tree in this sequence. These classes are the interfaces used to interact with the trees and mutational information stored in a tree sequence, for example as returned from a simulation or inferred from a set of DNA sequences. This library also provides methods for loading stored tree sequences, for example using tskit.load().

### The TreeSequence class¶

class tskit.TreeSequence[source]

A single tree sequence, as defined by the data model. A TreeSequence instance can be created from a set of tables using TableCollection.tree_sequence(), or loaded from a set of text files using tskit.load_text(), or loaded from a native binary file using tskit.load().

TreeSequences are immutable. To change the data held in a particular tree sequence, first get the table information as a TableCollection instance (using dump_tables()), edit those tables using the tables api, and create a new tree sequence using TableCollection.tree_sequence().

The trees() method iterates over all trees in a tree sequence, and the variants() method iterates over all sites and their genotypes.

Methods

 Fst(sample_sets[, indexes, windows, mode, …]) Computes “windowed” Fst between pairs of sets of nodes from sample_sets. Tajimas_D([sample_sets, windows, mode]) Computes Tajima’s D of sets of nodes from sample_sets in windows. Y1(sample_sets[, windows, mode, span_normalise]) Computes the ‘Y1’ statistic within each of the sets of nodes given by sample_sets. Y2(sample_sets[, indexes, windows, mode, …]) Computes the ‘Y2’ statistic between pairs of sets of nodes from sample_sets. Y3(sample_sets[, indexes, windows, mode, …]) Computes the ‘Y’ statistic between triples of sets of nodes from sample_sets. allele_frequency_spectrum([sample_sets, …]) Computes the allele frequency spectrum (AFS) in windows across the genome for with respect to the specified sample_sets. aslist(**kwargs) Returns the trees in this tree sequence as a list. at(position, **kwargs) Returns the tree covering the specified genomic location. at_index(index, **kwargs) Returns the tree at the specified index. breakpoints([as_array]) Returns the breakpoints along the chromosome, including the two extreme points 0 and L. coiterate(other, **kwargs) Returns an iterator over the pairs of trees for each distinct interval in the specified pair of tree sequences. count_topologies([sample_sets]) Returns a generator that produces the same distribution of topologies as Tree.count_topologies() but sequentially for every tree in a tree sequence. delete_intervals(intervals[, simplify, …]) Returns a copy of this tree sequence for which information in the specified list of genomic intervals has been deleted. delete_sites(site_ids[, record_provenance]) Returns a copy of this tree sequence with the specified sites (and their associated mutations) entirely removed. divergence(sample_sets[, indexes, windows, …]) Computes mean genetic divergence between (and within) pairs of sets of nodes from sample_sets. diversity([sample_sets, windows, mode, …]) Computes mean genetic diversity (also knowns as “Tajima’s pi”) in each of the sets of nodes from sample_sets. draw_svg([path, size, x_scale, time_scale, …]) Return an SVG representation of a tree sequence. draw_text(*[, node_labels, use_ascii, …]) Create a text representation of a tree sequence. dump(file_or_path[, zlib_compression]) Writes the tree sequence to the specified path or file object. A copy of the tables defining this tree sequence. dump_text([nodes, edges, sites, mutations, …]) Writes a text representation of the tables underlying the tree sequence to the specified connections. edge(id_) Returns the edge in this tree sequence with the specified ID. edge_diffs([include_terminal]) Returns an iterator over all the edges that are inserted and removed to build the trees as we move from left-to-right along the tree sequence. Returns an iterable sequence of all the edges in this tree sequence. equals(other, *[, ignore_metadata, …]) Returns True if self and other are equal. f2(sample_sets[, indexes, windows, mode, …]) Computes Patterson’s f3 statistic between two groups of nodes from sample_sets. f3(sample_sets[, indexes, windows, mode, …]) Computes Patterson’s f3 statistic between three groups of nodes from sample_sets. f4(sample_sets[, indexes, windows, mode, …]) Computes Patterson’s f4 statistic between four groups of nodes from sample_sets. first(**kwargs) Returns the first tree in this TreeSequence. Return the genealogical nearest neighbours (GNN) proportions for the given focal nodes, with reference to two or more sets of interest, averaged over all trees in the tree sequence. general_stat(W, f, output_dim[, windows, …]) Compute a windowed statistic from weights and a summary function. genetic_relatedness(sample_sets[, indexes, …]) Computes genetic relatedness between (and within) pairs of sets of nodes from sample_sets. genotype_matrix(*[, isolated_as_missing, …]) Returns an $$m \times n$$ numpy array of the genotypes in this tree sequence, where $$m$$ is the number of sites and $$n$$ the number of samples. haplotypes(*[, isolated_as_missing, …]) Returns an iterator over the strings of haplotypes that result from the trees and mutations in this tree sequence. individual(id_) Returns the individual in this tree sequence with the specified ID. Returns an iterable sequence of all the individuals in this tree sequence. kc_distance(other[, lambda_]) Returns the average Tree.kc_distance() between pairs of trees along the sequence whose intervals overlap. keep_intervals(intervals[, simplify, …]) Returns a copy of this tree sequence which includes only information in the specified list of genomic intervals. last(**kwargs) Returns the last tree in this TreeSequence. ltrim([record_provenance]) Returns a copy of this tree sequence with a potentially changed coordinate system, such that empty regions (i.e., those not covered by any edge) at the start of the tree sequence are trimmed away, and the leftmost edge starts at position 0. mean_descendants(sample_sets) Computes for every node the mean number of samples in each of the sample_sets that descend from that node, averaged over the portions of the genome for which the node is ancestral to any sample. migration(id_) Returns the migration in this tree sequence with the specified ID. Returns an iterable sequence of all the migrations in this tree sequence. mutation(id_) Returns the mutation in this tree sequence with the specified ID. Returns an iterator over all the mutations in this tree sequence. node(id_) Returns the node in this tree sequence with the specified ID. Returns an iterable sequence of all the nodes in this tree sequence. pairwise_diversity([samples]) Returns the pairwise nucleotide site diversity, the average number of sites that differ between a randomly chosen pair of samples. population(id_) Returns the population in this tree sequence with the specified ID. Returns an iterable sequence of all the populations in this tree sequence. Returns an iterable sequence of all the provenances in this tree sequence. rtrim([record_provenance]) Returns a copy of this tree sequence with the sequence_length property reset so that the sequence ends at the end of the rightmost edge. sample_count_stat(sample_sets, f, output_dim) Compute a windowed statistic from sample counts and a summary function. samples([population, population_id]) Returns an array of the sample node IDs in this tree sequence. segregating_sites([sample_sets, windows, …]) Computes the density of segregating sites for each of the sets of nodes from sample_sets, and related quantities. simplify([samples, map_nodes, …]) Returns a simplified tree sequence that retains only the history of the nodes given in the list samples. site(id_) Returns the site in this tree sequence with the specified ID. Returns an iterable sequence of all the sites in this tree sequence. subset(nodes[, record_provenance, …]) Returns a tree sequence containing only information directly referencing the provided list of nodes to retain. Return a macs encoding of this tree sequence. to_nexus([precision]) Returns a nexus encoding of this tree sequence. trait_correlation(W[, windows, mode, …]) Computes the mean squared correlations between each of the columns of W (the “phenotypes”) and inheritance along the tree sequence. trait_covariance(W[, windows, mode, …]) Computes the mean squared covariances between each of the columns of W (the “phenotypes”) and inheritance along the tree sequence. trait_linear_model(W[, Z, windows, mode, …]) Finds the relationship between trait and genotype after accounting for covariates. trait_regression(*args, **kwargs) Deprecated synonym for trait_linear_model. trees([tracked_samples, sample_lists, …]) Returns an iterator over the trees in this tree sequence. trim([record_provenance]) Returns a copy of this tree sequence with any empty regions (i.e., those not covered by any edge) on the right and left trimmed away. union(other, node_mapping[, …]) Returns an expanded tree sequence which contains the node-wise union of self and other, obtained by adding the non-shared portions of other onto self. variants(*[, as_bytes, samples, …]) Returns an iterator over the variants in this tree sequence. write_vcf(output[, ploidy, contig_id, …]) Writes a VCF formatted file to the specified file-like object.

Attributes

 max_root_time Returns the time of the oldest root in any of the trees in this tree sequence. metadata The decoded metadata for this TreeSequence. metadata_schema The tskit.MetadataSchema for this TreeSequence. nbytes Returns the total number of bytes required to store the data in this tree sequence. num_edges Returns the number of edges in this tree sequence. num_individuals Returns the number of individuals in this tree sequence. num_migrations Returns the number of migrations in this tree sequence. num_mutations Returns the number of mutations in this tree sequence. num_nodes Returns the number of nodes in this tree sequence. num_populations Returns the number of populations in this tree sequence. num_provenances Returns the number of provenances in this tree sequence. num_samples Returns the number of samples in this tree sequence. num_sites Returns the number of sites in this tree sequence. num_trees Returns the number of distinct trees in this tree sequence. sequence_length Returns the sequence length in this tree sequence. table_metadata_schemas The set of metadata schemas for the tables in this tree sequence. tables A copy of the tables underlying this tree sequence. tables_dict Returns a dictionary mapping names to tables in the underlying TableCollection.
Fst(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes “windowed” Fst between pairs of sets of nodes from sample_sets. Operates on k = 2 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

For sample sets X and Y, if d(X, Y) is the divergence between X and Y, and d(X) is the diversity of X, then what is computed is

Fst = 1 - 2 * (d(X) + d(Y)) / (d(X) + 2 * d(X, Y) + d(Y))


What is computed for diversity and divergence depends on mode; see those functions for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

Tajimas_D(sample_sets=None, windows=None, mode='site')[source]

Computes Tajima’s D of sets of nodes from sample_sets in windows. Please see the one-way statistics section for details on how the sample_sets argument is interpreted and how it interacts with the dimensions of the output array. See the statistics interface section for details on windows, mode, and return value. Operates on k = 1 sample sets at a time. For a sample set X of n nodes, if and T is the mean number of pairwise differing sites in X and S is the number of sites segregating in X (computed with diversity and segregating sites, respectively, both not span normalised), then Tajima’s D is

D = (T - S / h) / sqrt(a * S + (b / c) * S * (S - 1))
h = 1 + 1 / 2 + ... + 1 / (n - 1)
g = 1 + 1 / 2 ** 2 + ... + 1 / (n - 1) ** 2
a = (n + 1) / (3 * (n - 1) * h) - 1 / h ** 2
b = 2 * (n ** 2 + n + 3) / (9 * n * (n - 1)) - (n + 2) / (h * n) + g / h ** 2
c = h ** 2 + g


What is computed for diversity and divergence depends on mode; see those functions for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

Returns

A ndarray with shape equal to (num windows, num statistics).

Y1(sample_sets, windows=None, mode='site', span_normalise=True)[source]

Computes the ‘Y1’ statistic within each of the sets of nodes given by sample_sets. Please see the one-way statistics section for details on how the sample_sets argument is interpreted and how it interacts with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value. Operates on k = 1 sample set at a time.

What is computed depends on mode. Each is computed exactly as Y3, except that the average is across a randomly chosen trio of samples (a1, a2, a3) all chosen without replacement from the same sample set. See Y3 for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

Y2(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes the ‘Y2’ statistic between pairs of sets of nodes from sample_sets. Operates on k = 2 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. Each is computed exactly as Y3, except that the average across randomly chosen trios of samples (a, b1, b2), where a is chosen from the first sample set, and b1, b2 are chosen (without replacement) from the second sample set. See Y3 for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

Y3(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes the ‘Y’ statistic between triples of sets of nodes from sample_sets. Operates on k = 3 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. Each is an average across randomly chosen trios of samples (a, b, c), one from each sample set:

“site”

The average density of sites at which a differs from b and c, per unit of chromosome length.

“branch”

The average length of all branches that separate a from b and c (in units of time).

“node”

For each node, the average proportion of the window on which a inherits from that node but b and c do not, or vice-versa.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 3-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

allele_frequency_spectrum(sample_sets=None, windows=None, mode='site', span_normalise=True, polarised=False)[source]

Computes the allele frequency spectrum (AFS) in windows across the genome for with respect to the specified sample_sets. See the statistics interface section for details on sample sets, windows, mode, span normalise, polarised, and return value. and see Allele frequency spectra for examples of how to use this method.

Similar to other windowed stats, the first dimension in the returned array corresponds to windows, such that result[i] is the AFS in the ith window. The AFS in each window is a k-dimensional numpy array, where k is the number of input sample sets, such that result[i, j0, j1, ...] is the value associated with frequency j0 in sample_sets[0], j1 in sample_sets[1], etc, in window i. From here, we will assume that afs corresponds to the result in a single window, i.e., afs = result[i].

If a single sample set is specified, the allele frequency spectrum within this set is returned, such that afs[j] is the value associated with frequency j. Thus, singletons are counted in afs[1], doubletons in afs[2], and so on. The zeroth entry counts alleles or branches not seen in the samples but that are polymorphic among the rest of the samples of the tree sequence; likewise, the last entry counts alleles fixed in the sample set but polymorphic in the entire set of samples. Please see the Zeroth and final entries in the AFS for an illustration.

Warning

Please note that singletons are not counted in the initial entry in each AFS array (i.e., afs[0]), but in afs[1].

If sample_sets is None (the default), the allele frequency spectrum for all samples in the tree sequence is returned.

If more than one sample set is specified, the joint allele frequency spectrum within windows is returned. For example, if we set sample_sets = [S0, S1], then afs[1, 2] counts the number of sites that are singletons within S0 and doubletons in S1. The dimensions of the output array will be [num_windows] + [1 + len(S) for S in sample_sets].

If polarised is False (the default) the AFS will be folded, so that the counts do not depend on knowing which allele is ancestral. If folded, the frequency spectrum for a single sample set S has afs[j] = 0 for all j > len(S) / 2, so that alleles at frequency j and len(S) - j both add to the same entry. If there is more than one sample set, the returned array is “lower triangular” in a similar way. For more details, especially about handling of multiallelic sites, see Allele frequency spectrum.

What is computed depends on mode:

“site”

The number of alleles at a given frequency within the specified sample sets for each window, per unit of sequence length. To obtain the total number of alleles, set span_normalise to False.

“branch”

The total length of branches in the trees subtended by subsets of the specified sample sets, per unit of sequence length. To obtain the total, set span_normalise to False.

“node”

Not supported for this method (raises a ValueError).

For example, suppose that S0 is a list of 5 sample IDs, and S1 is a list of 3 other sample IDs. Then afs = ts.allele_frequency_spectrum([S0, S1], mode=”site”, span_normalise=False) will be a 5x3 numpy array, and if there are six alleles that are present in only one sample of S0 but two samples of S1, then afs[1,2] will be equal to 6. Similarly, branch_afs = ts.allele_frequency_spectrum([S0, S1], mode=”branch”, span_normalise=False) will also be a 5x3 array, and branch_afs[1,2] will be the total area (i.e., length times span) of all branches that are above exactly one sample of S0 and two samples of S1.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of samples to compute the joint allele frequency

• windows (list) – An increasing list of breakpoints between windows along the genome.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A (k + 1) dimensional numpy array, where k is the number of sample sets specified.

aslist(**kwargs)[source]

Returns the trees in this tree sequence as a list. Each tree is represented by a different instance of Tree. As such, this method is inefficient and may use a large amount of memory, and should not be used when performance is a consideration. The trees() method is the recommended way to efficiently iterate over the trees in a tree sequence.

Parameters

**kwargs – Further arguments used as parameters when constructing the returned trees. For example ts.aslist(sample_lists=True) will result in a list of Tree instances created with sample_lists=True.

Returns

A list of the trees in this tree sequence.

Return type

list

at(position, **kwargs)[source]

Returns the tree covering the specified genomic location. The returned tree will have tree.interval.left <= position < tree.interval.right. See also Tree.seek().

Parameters
• position (float) – A genomic location.

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example ts.at(2.5, sample_lists=True) will result in a Tree created with sample_lists=True.

Returns

A new instance of Tree positioned to cover the specified genomic location.

Return type

Tree

at_index(index, **kwargs)[source]

Returns the tree at the specified index. See also Tree.seek_index().

Parameters
• index (int) – The index of the required tree.

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example ts.at_index(4, sample_lists=True) will result in a Tree created with sample_lists=True.

Returns

A new instance of Tree positioned at the specified index.

Return type

Tree

breakpoints(as_array=False)[source]

Returns the breakpoints along the chromosome, including the two extreme points 0 and L. This is equivalent to

>>> iter([0] + [t.interval.right for t in self.trees()])


By default we return an iterator over the breakpoints as Python float objects; if as_array is True we return them as a numpy array.

Note that the as_array form will be more efficient and convenient in most cases; the default iterator behaviour is mainly kept to ensure compatibility with existing code.

Parameters

as_array (bool) – If True, return the breakpoints as a numpy array.

Returns

The breakpoints defined by the tree intervals along the sequence.

Return type
coiterate(other, **kwargs)[source]

Returns an iterator over the pairs of trees for each distinct interval in the specified pair of tree sequences.

Parameters
• other (TreeSequence) – The other tree sequence from which to take trees. The sequence length must be the same as the current tree sequence.

• **kwargs – Further named arguments that will be passed to the trees() method when constructing the returned trees.

Returns

An iterator returning successive tuples of the form (interval, tree_self, tree_other). For example, the first item returned will consist of an tuple of the initial interval, the first tree of the current tree sequence, and the first tree of the other tree sequence; the .left attribute of the initial interval will be 0 and the .right attribute will be the smallest non-zero breakpoint of the 2 tree sequences.

Return type
count_topologies(sample_sets=None)[source]

Returns a generator that produces the same distribution of topologies as Tree.count_topologies() but sequentially for every tree in a tree sequence. For use on a tree sequence this method is much faster than computing the result independently per tree.

Warning

The interface for this method is preliminary and may be subject to backwards incompatible changes in the near future.

Parameters

sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

Return type
Raises

ValueError – If nodes in sample_sets are invalid or are internal samples.

delete_intervals(intervals, simplify=True, record_provenance=True)[source]

Returns a copy of this tree sequence for which information in the specified list of genomic intervals has been deleted. Edges spanning these intervals are truncated or deleted, and sites and mutations falling within them are discarded. Note that it is the information in the intervals that is deleted, not the intervals themselves, so in particular, all samples will be isolated in the deleted intervals.

Note that node IDs may change as a result of this operation, as by default simplify() is called on the returned tree sequence to remove redundant nodes. If you wish to map node IDs onto the same nodes before and after this method has been called, specify simplify=False.

Parameters
• intervals (array_like) – A list (start, end) pairs describing the genomic intervals to delete. Intervals must be non-overlapping and in increasing order. The list of intervals must be interpretable as a 2D numpy array with shape (N, 2), where N is the number of intervals.

• simplify (bool) – If True, return a simplified tree sequence where nodes no longer used are discarded. (Default: True).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

Return type

TreeSequence

delete_sites(site_ids, record_provenance=True)[source]

Returns a copy of this tree sequence with the specified sites (and their associated mutations) entirely removed. The site IDs do not need to be in any particular order, and specifying the same ID multiple times does not have any effect (i.e., calling tree_sequence.delete_sites([0, 1, 1]) has the same effect as calling tree_sequence.delete_sites([0, 1]).

Parameters
• site_ids (list[int]) – A list of site IDs specifying the sites to remove.

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

divergence(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes mean genetic divergence between (and within) pairs of sets of nodes from sample_sets. Operates on k = 2 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

As a special case, an index (j, j) will compute the diversity of sample_set[j].

What is computed depends on mode:

“site”

Mean pairwise genetic divergence: the average across distinct, randomly chosen pairs of chromosomes (one from each sample set), of the density of sites at which the two carry different alleles, per unit of chromosome length.

“branch”

Mean distance in the tree: the average across distinct, randomly chosen pairs of chromosomes (one from each sample set) and locations in the window, of the mean distance in the tree between the two samples (in units of time).

“node”

For each node, the proportion of genome on which the node is an ancestor to only one of a random pair (one from each sample set), averaged over choices of pair.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

diversity(sample_sets=None, windows=None, mode='site', span_normalise=True)[source]

Computes mean genetic diversity (also knowns as “Tajima’s pi”) in each of the sets of nodes from sample_sets. Please see the one-way statistics section for details on how the sample_sets argument is interpreted and how it interacts with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

Note that this quantity can also be computed by the divergence method.

What is computed depends on mode:

“site”

Mean pairwise genetic diversity: the average across distinct, randomly chosen pairs of chromosomes, of the density of sites at which the two carry different alleles, per unit of chromosome length.

“branch”

Mean distance in the tree: the average across distinct, randomly chosen pairs of chromosomes and locations in the window, of the mean distance in the tree between the two samples (in units of time).

“node”

For each node, the proportion of genome on which the node is an ancestor to only one of a random pair from the sample set, averaged over choices of pair.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A numpy array.

draw_svg(path=None, *, size=None, x_scale=None, time_scale=None, tree_height_scale=None, node_labels=None, mutation_labels=None, root_svg_attributes=None, style=None, order=None, force_root_branch=None, symbol_size=None, x_axis=None, x_label=None, x_lim=None, y_axis=None, y_label=None, y_ticks=None, y_gridlines=None, **kwargs)[source]

Return an SVG representation of a tree sequence. See the visualization tutorial for more details.

Parameters
• path (str) – The path to the file to write the output. If None, do not write to file.

• size (tuple(int, int)) – A tuple of (width, height) giving the width and height of the produced SVG drawing in abstract user units (usually interpreted as pixels on display).

• x_scale (str) – Control how the X axis is drawn. If “physical” (the default) the axis scales linearly with physical distance along the sequence, background shading is used to indicate the position of the trees along the X axis, and sites (with associated mutations) are marked at the appropriate physical position on axis line. If “treewise”, each axis tick corresponds to a tree boundary, which are positioned evenly along the axis, so that the X axis is of variable scale, no background scaling is required, and site positions are not marked on the axis.

• time_scale (str) – Control how height values for nodes are computed. If this is equal to "time", node heights are proportional to their time values (this is the default). If this is equal to "log_time", node heights are proportional to their log(time) values. If it is equal to "rank", node heights are spaced equally according to their ranked times.

• tree_height_scale (str) – Deprecated alias for time_scale. (Deprecated in 0.3.6)

• node_labels (dict(int, str)) – If specified, show custom labels for the nodes (specified by ID) that are present in this map; any nodes not present will not have a label.

• mutation_labels (dict(int, str)) – If specified, show custom labels for the mutations (specified by ID) that are present in the map; any mutations not present will not have a label.

• root_svg_attributes (dict) – Additional attributes, such as an id, that will be embedded in the root <svg> tag of the generated drawing.

• style (str) – A css string that will be included in the <style> tag of the generated svg.

• order (str) – The left-to-right ordering of child nodes in each drawn tree. This can be either: "minlex", which minimises the differences between adjacent trees (see also the "minlex_postorder" traversal order for the nodes() method); or "tree" which draws trees in the left-to-right order defined by the quintuply linked tree structure. If not specified or None, this defaults to "minlex".

• force_root_branch (bool) – If True plot a branch (edge) above every tree root in the tree sequence. If None (default) then only plot such root branches if any root in the tree sequence has a mutation above it.

• symbol_size (float) – Change the default size of the node and mutation plotting symbols. If None (default) use a standard size.

• x_axis (bool) – Should the plot have an X axis line, showing the positions of trees along the genome. The scale used is determined by the x_scale parameter. If None (default) plot an X axis.

• x_label (str) – Place a label under the plot. If None (default) and there is an X axis, create and place an appropriate label.

• x_lim (list) – A list of size two giving the genomic positions between which trees should be plotted. If the first is None, then plot from the first non-empty region of the tree sequence. If the second is None, then plot up to the end of the last non-empty region of the tree sequence. The default value x_lim=None is shorthand for the list [None, None]. If numerical values are given, then regions outside the interval have all information discarded: this means that mutations outside the interval will not be shown. To force display of the entire tree sequence, including empty flanking regions, specify x_lim=[0, ts.sequence_length].

• y_axis (bool) – Should the plot have an Y axis line, showing time (or ranked node time if time_scale="rank". If None (default) do not plot a Y axis.

• y_label (str) – Place a label to the left of the plot. If None (default) and there is a Y axis, create and place an appropriate label.

• y_ticks (list) – A list of Y values at which to plot tickmarks ([] gives no tickmarks). If None, plot one tickmark for each unique node value.

• y_gridlines (bool) – Whether to plot horizontal lines behind the tree at each y tickmark.

Returns

An SVG representation of a tree sequence.

Return type

str

Note

Technically, x_lim[0] specifies a minimum value for the start of the X axis, and x_lim[1] specifies a maximum value for the end. This is only relevant if the tree sequence contains “empty” regions with no edges or mutations. In this case if x_lim[0] lies strictly within an empty region (i.e., empty_tree.interval.left < x_lim[0] < empty_tree.interval.right) then that tree will not be plotted on the left hand side, and the X axis will start at empty_tree.interval.right. Similarly, if x_lim[1] lies strictly within an empty region then that tree will not be plotted on the right hand side, and the X axis will end at empty_tree.interval.left

draw_text(*, node_labels=None, use_ascii=False, time_label_format=None, position_label_format=None, order=None, **kwargs)[source]

Create a text representation of a tree sequence.

Parameters
• node_labels (dict) – If specified, show custom labels for the nodes that are present in the map. Any nodes not specified in the map will not have a node label.

• use_ascii (bool) – If False (default) then use unicode box drawing characters to render the tree. If True, use plain ascii characters, which look cruder but are less susceptible to misalignment or font substitution. Alternatively, if you are having alignment problems with Unicode, you can try out the solution documented here.

• time_label_format (str) – A python format string specifying the format (e.g. number of decimal places or significant figures) used to print the numerical time values on the time axis. If None, this defaults to "{:.2f}".

• position_label_format (str) – A python format string specifying the format (e.g. number of decimal places or significant figures) used to print genomic positions. If None, this defaults to "{:.2f}".

• order (str) – The left-to-right ordering of child nodes in the drawn tree. This can be either: "minlex", which minimises the differences between adjacent trees (see also the "minlex_postorder" traversal order for the nodes() method); or "tree" which draws trees in the left-to-right order defined by the quintuply linked tree structure. If not specified or None, this defaults to "minlex".

Returns

A text representation of a tree sequence.

Return type

str

dump(file_or_path, zlib_compression=False)[source]

Writes the tree sequence to the specified path or file object.

Parameters
• file_or_path (str) – The file object or path to write the TreeSequence to.

• zlib_compression (bool) – This parameter is deprecated and ignored.

dump_tables()[source]

A copy of the tables defining this tree sequence.

Returns

A TableCollection containing all tables underlying the tree sequence.

Return type

TableCollection

dump_text(nodes=None, edges=None, sites=None, mutations=None, individuals=None, populations=None, provenances=None, precision=6, encoding='utf8', base64_metadata=True)[source]

Writes a text representation of the tables underlying the tree sequence to the specified connections.

If Base64 encoding is not used, then metadata will be saved directly, possibly resulting in errors reading the tables back in if metadata includes whitespace.

Parameters
• nodes (io.TextIOBase) – The file-like object (having a .write() method) to write the NodeTable to.

• edges (io.TextIOBase) – The file-like object to write the EdgeTable to.

• sites (io.TextIOBase) – The file-like object to write the SiteTable to.

• mutations (io.TextIOBase) – The file-like object to write the MutationTable to.

• individuals (io.TextIOBase) – The file-like object to write the IndividualTable to.

• populations (io.TextIOBase) – The file-like object to write the PopulationTable to.

• provenances (io.TextIOBase) – The file-like object to write the ProvenanceTable to.

• precision (int) – The number of digits of precision.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

edge(id_)[source]

Returns the edge in this tree sequence with the specified ID.

Return type

Edge

edge_diffs(include_terminal=False)[source]

Returns an iterator over all the edges that are inserted and removed to build the trees as we move from left-to-right along the tree sequence. Each iteration yields a named tuple consisting of 3 values, (interval, edges_out, edges_in). The first value, interval, is the genomic interval (left, right) covered by the incoming tree (see Tree.interval). The second, edges_out is a list of the edges that were just-removed to create the tree covering the interval (hence edges_out will always be empty for the first tree). The last value, edges_in, is a list of edges that were just inserted to construct the tree covering the current interval.

The edges returned within each edges_in list are ordered by ascending time of the parent node, then ascending parent id, then ascending child id. The edges within each edges_out list are the reverse order (e.g. descending parent time, parent id, then child_id). This means that within each list, edges with the same parent appear consecutively.

Parameters

include_terminal (bool) – If False (default), the iterator terminates after the final interval in the tree sequence (i.e., it does not report a final removal of all remaining edges), and the number of iterations will be equal to the number of trees in the tree sequence. If True, an additional iteration takes place, with the last edges_out value reporting all the edges contained in the final tree (with both left and right equal to the sequence length).

Returns

An iterator over the (interval, edges_out, edges_in) tuples. This is a named tuple, so the 3 values can be accessed by position (e.g. returned_tuple[0]) or name (e.g. returned_tuple.interval).

Return type

collections.abc.Iterable

edges()[source]

Returns an iterable sequence of all the edges in this tree sequence. Edges are returned in the order required for a valid tree sequence. So, edges are guaranteed to be ordered such that (a) all parents with a given ID are contiguous; (b) edges are returned in non-decreasing order of parent time ago; (c) within the edges for a given parent, edges are sorted first by child ID and then by left coordinate.

Returns

An iterable sequence of all edges.

Return type

Sequence(Edge)

equals(other, *, ignore_metadata=False, ignore_ts_metadata=False, ignore_provenance=False, ignore_timestamps=False)[source]

Returns True if self and other are equal. Uses the underlying table equality, see TableCollection.equals() for details and options.

f2(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes Patterson’s f3 statistic between two groups of nodes from sample_sets. Operates on k = 2 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. Each works exactly as f4, except the average is across randomly chosen set of four samples (a1, b1; a2, b2), with a1 and a2 both chosen (without replacement) from the first sample set and b1 and b2 chosen randomly without replacement from the second sample set. See f4 for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

f3(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes Patterson’s f3 statistic between three groups of nodes from sample_sets. Operates on k = 3 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. Each works exactly as f4, except the average is across randomly chosen set of four samples (a1, b; a2, c), with a1 and a2 both chosen (without replacement) from the first sample set. See f4 for more details.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 3-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

f4(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True)[source]

Computes Patterson’s f4 statistic between four groups of nodes from sample_sets. Operates on k = 4 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. Each is an average across randomly chosen set of four samples (a, b; c, d), one from each sample set:

“site”

The average density of sites at which a and c agree but differs from b and d, minus the average density of sites at which a and d agree but differs from b and c, per unit of chromosome length.

“branch”

The average length of all branches that separate a and c from b and d, minus the average length of all branches that separate a and d from b and c (in units of time).

“node”

For each node, the average proportion of the window on which a and c inherit from that node but b and d do not, or vice-versa, minus the average proportion of the window on which a and d inherit from that node but b and c do not, or vice-versa.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 4-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

first(**kwargs)[source]

Returns the first tree in this TreeSequence. To iterate over all trees in the sequence, use the trees() method.

Parameters

**kwargs – Further arguments used as parameters when constructing the returned Tree. For example ts.first(sample_lists=True) will result in a Tree created with sample_lists=True.

Returns

The first tree in this tree sequence.

Return type
genealogical_nearest_neighbours(focal, sample_sets, num_threads=0)[source]

Return the genealogical nearest neighbours (GNN) proportions for the given focal nodes, with reference to two or more sets of interest, averaged over all trees in the tree sequence.

The GNN proportions for a focal node in a single tree are given by first finding the most recent common ancestral node $$a$$ between the focal node and any other node present in the reference sets. The GNN proportion for a specific reference set, $$S$$ is the number of nodes in $$S$$ that descend from $$a$$, as a proportion of the total number of descendant nodes in any of the reference sets.

For example, consider a case with 2 sample sets, $$S_1$$ and $$S_2$$. For a given tree, $$a$$ is the node that includes at least one descendant in $$S_1$$ or $$S_2$$ (not including the focal node). If the descendants of $$a$$ include some nodes in $$S_1$$ but no nodes in $$S_2$$, then the GNN proportions for that tree will be 100% $$S_1$$ and 0% $$S_2$$, or $$[1.0, 0.0]$$.

For a given focal node, the GNN proportions returned by this function are an average of the GNNs for each tree, weighted by the genomic distance spanned by that tree.

For an precise mathematical definition of GNN, see https://doi.org/10.1101/458067

Note

The reference sets need not include all the samples, hence the most recent common ancestral node of the reference sets, $$a$$, need not be the immediate ancestor of the focal node. If the reference sets only comprise sequences from relatively distant individuals, the GNN statistic may end up as a measure of comparatively distant ancestry, even for tree sequences that contain many closely related individuals.

Warning

The interface for this method is preliminary and may be subject to backwards incompatible changes in the near future. The long-term stable API for this method will be consistent with other Statistics.

Parameters
• focal (list) – A list of $$n$$ nodes whose GNNs should be calculated.

• sample_sets (list) – A list of $$m$$ lists of node IDs.

Returns

An $$n$$ by $$m$$ array of focal nodes by GNN proportions. Every focal node corresponds to a row. The numbers in each row corresponding to the GNN proportion for each of the passed-in reference sets. Rows therefore sum to one.

Return type

numpy.ndarray

general_stat(W, f, output_dim, windows=None, polarised=False, mode=None, span_normalise=True, strict=True)[source]

Compute a windowed statistic from weights and a summary function. See the statistics interface section for details on windows, mode, span normalise, and return value. On each tree, this propagates the weights W up the tree, so that the “weight” of each node is the sum of the weights of all samples at or below the node. Then the summary function f is applied to the weights, giving a summary for each node in each tree. How this is then aggregated depends on mode:

“site”

Adds together the total summary value across all alleles in each window.

“branch”

Adds together the summary value for each node, multiplied by the length of the branch above the node and the span of the tree.

“node”

Returns each node’s summary value added across trees and multiplied by the span of the tree.

Both the weights and the summary can be multidimensional: if W has k columns, and f takes a k-vector and returns an m-vector, then the output will be m-dimensional for each node or window (depending on “mode”).

Note

The summary function f should return zero when given both 0 and the total weight (i.e., f(0) = 0 and f(np.sum(W, axis=0)) = 0), unless strict=False. This is necessary for the statistic to be unaffected by parts of the tree sequence ancestral to none or all of the samples, respectively.

Parameters
• W (numpy.ndarray) – An array of values with one row for each sample and one column for each weight.

• f – A function that takes a one-dimensional array of length equal to the number of columns of W and returns a one-dimensional array.

• output_dim (int) – The length of f’s return value.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• polarised (bool) – Whether to leave the ancestral state out of computations: see Statistics for more details.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

• strict (bool) – Whether to check that f(0) and f(total weight) are zero.

Returns

A ndarray with shape equal to (num windows, num statistics).

genetic_relatedness(sample_sets, indexes=None, windows=None, mode='site', span_normalise=True, polarised=False, proportion=True)[source]

Computes genetic relatedness between (and within) pairs of sets of nodes from sample_sets. Operates on k = 2 sample sets at a time; please see the multi-way statistics section for details on how the sample_sets and indexes arguments are interpreted and how they interact with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, polarised, and return value.

What is computed depends on mode:

“site”

Number of pairwise allelic matches in the window between two sample sets relative to the rest of the sample sets. To be precise, let m(u,v) denote the total number of alleles shared between nodes u and v, and let m(I,J) be the sum of m(u,v) over all nodes u in sample set I and v in sample set J. Let S and T be independently chosen sample sets. Then, for sample sets I and J, this computes E[m(I,J) - m(I,S) - m(J,T) + m(S,T)]. This can also be seen as the covariance of a quantitative trait determined by additive contributions from the genomes in each sample set. Let each allele be associated with an effect drawn from a N(0,1/2) distribution, and let the trait value of a sample set be the sum of its allele effects. Then, this computes the covariance between the trait values of two sample sets. For example, to compute covariance between the traits of diploid individuals, each sample set would be the pair of genomes of each individual; if proportion=True, this then corresponds to $$K_{c0}$$ in Speed & Balding (2014).

“branch”

Total area of branches in the window ancestral to pairs of samples in two sample sets relative to the rest of the sample sets. To be precise, let B(u,v) denote the total area of all branches ancestral to nodes u and v, and let B(I,J) be the sum of B(u,v) over all nodes u in sample set I and v in sample set J. Let S and T be two independently chosen sample sets. Then for sample sets I and J, this computes E[B(I,J) - B(I,S) - B(J,T) + B(S,T)].

“node”

For each node, the proportion of the window over which pairs of samples in two sample sets are descendants, relative to the rest of the sample sets. To be precise, for each node n, let N(u,v) denote the proportion of the window over which samples u and v are descendants of n, and let and let N(I,J) be the sum of N(u,v) over all nodes u in sample set I and v in sample set J. Let S and T be two independently chosen sample sets. Then for sample sets I and J, this computes E[N(I,J) - N(I,S) - N(J,T) + N(S,T)].

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• indexes (list) – A list of 2-tuples, or None.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

• proportion (bool) – Whether to divide the result by segregating_sites(), called with the same windows and mode (defaults to True). Note that this counts sites that are segregating between any of the samples of any of the sample sets (rather than segregating between all of the samples of the tree sequence).

Returns

A ndarray with shape equal to (num windows, num statistics).

genotype_matrix(*, isolated_as_missing=None, alleles=None, impute_missing_data=None)[source]

Returns an $$m \times n$$ numpy array of the genotypes in this tree sequence, where $$m$$ is the number of sites and $$n$$ the number of samples. The genotypes are the indexes into the array of alleles, as described for the Variant class.

If isolated samples are present at a given site without mutations above them, they will be interpreted as missing data the genotypes array will contain a special value MISSING_DATA (-1) to identify these missing samples.

Such samples are treated as missing data by default, but if isolated_as_missing is set to to False, they will not be treated as missing, and so assigned the ancestral state. This was the default behaviour in versions prior to 0.2.0. Prior to 0.3.0 the impute_missing_data argument controlled this behaviour.

Warning

This method can consume a very large amount of memory! If all genotypes are not needed at once, it is usually better to access them sequentially using the variants() iterator.

Parameters
• isolated_as_missing (bool) – If True, the allele assigned to missing samples (i.e., isolated samples without mutations) is the missing_data_character. If False, missing samples will be assigned the ancestral state. Default: True.

• alleles (tuple) – A tuple of strings describing the encoding of alleles to genotype values. At least one allele must be provided. If duplicate alleles are provided, output genotypes will always be encoded as the first occurrence of the allele. If None (the default), the alleles are encoded as they are encountered during genotype generation.

• impute_missing_data (bool) – Deprecated in 0.3.0. Use isolated_as_missing, but inverting value. Will be removed in a future version

Returns

The full matrix of genotypes.

Return type

numpy.ndarray (dtype=np.int8)

haplotypes(*, isolated_as_missing=None, missing_data_character='-', impute_missing_data=None)[source]

Returns an iterator over the strings of haplotypes that result from the trees and mutations in this tree sequence. Each haplotype string is guaranteed to be of the same length. A tree sequence with $$n$$ samples and $$s$$ sites will return a total of $$n$$ strings of $$s$$ alleles concatenated together, where an allele consists of a single ascii character (tree sequences that include alleles which are not a single character in length, or where the character is non-ascii, will raise an error). The first string returned is the haplotype for sample 0, and so on.

The alleles at each site must be represented by single byte characters, (i.e., variants must be single nucleotide polymorphisms, or SNPs), hence the strings returned will all be of length $$s$$, and for a haplotype h, the value of h[j] will be the observed allelic state at site j.

If isolated_as_missing is True (the default), isolated samples without mutations directly above them will be treated as missing data and will be represented in the string by the missing_data_character. If instead it is set to False, missing data will be assigned the ancestral state (unless they have mutations directly above them, in which case they will take the most recent derived mutational state for that node). This was the default behaviour in versions prior to 0.2.0. Prior to 0.3.0 the impute_missing_data argument controlled this behaviour.

See also the variants() iterator for site-centric access to sample genotypes.

Warning

For large datasets, this method can consume a very large amount of memory! To output all the sample data, it is more efficient to iterate over sites rather than over samples. If you have a large dataset but only want to output the haplotypes for a subset of samples, it may be worth calling simplify() to reduce tree sequence down to the required samples before outputting haplotypes.

Returns

An iterator over the haplotype strings for the samples in this tree sequence.

Parameters
• isolated_as_missing (bool) – If True, the allele assigned to missing samples (i.e., isolated samples without mutations) is the missing_data_character. If False, missing samples will be assigned the ancestral state. Default: True.

• missing_data_character (str) – A single ascii character that will be used to represent missing data. If any normal allele contains this character, an error is raised. Default: ‘-‘.

• impute_missing_data (bool) – Deprecated in 0.3.0. Use isolated_as_missing, but inverting value. Will be removed in a future version

Return type

collections.abc.Iterable

Raises

TypeError if the missing_data_character or any of the alleles at a site or the are not a single ascii character.

Raises

ValueError if the missing_data_character exists in one of the alleles

individual(id_)[source]

Returns the individual in this tree sequence with the specified ID.

Return type

Individual

individuals()[source]

Returns an iterable sequence of all the individuals in this tree sequence.

Returns

An iterable sequence of all individuals.

Return type

Sequence(Individual)

kc_distance(other, lambda_=0.0)[source]

Returns the average Tree.kc_distance() between pairs of trees along the sequence whose intervals overlap. The average is weighted by the fraction of the sequence on which each pair of trees overlap.

Parameters
• other (TreeSequence) – The other tree sequence to compare to.

• lambda (float) – The KC metric lambda parameter determining the relative weight of topology and branch length.

Returns

The computed KC distance between this tree sequence and other.

Return type

float

keep_intervals(intervals, simplify=True, record_provenance=True)[source]

Returns a copy of this tree sequence which includes only information in the specified list of genomic intervals. Edges are truncated to lie within these intervals, and sites and mutations falling outside these intervals are discarded. Note that it is the information outside the intervals that is deleted, not the intervals themselves, so in particular, all samples will be isolated outside of the retained intervals.

Note that node IDs may change as a result of this operation, as by default simplify() is called on the returned tree sequence to remove redundant nodes. If you wish to map node IDs onto the same nodes before and after this method has been called, specify simplify=False.

Parameters
• intervals (array_like) – A list (start, end) pairs describing the genomic intervals to keep. Intervals must be non-overlapping and in increasing order. The list of intervals must be interpretable as a 2D numpy array with shape (N, 2), where N is the number of intervals.

• simplify (bool) – If True, return a simplified tree sequence where nodes no longer used are discarded. (Default: True).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

Return type

TreeSequence

last(**kwargs)[source]

Returns the last tree in this TreeSequence. To iterate over all trees in the sequence, use the trees() method.

Parameters

**kwargs – Further arguments used as parameters when constructing the returned Tree. For example ts.first(sample_lists=True) will result in a Tree created with sample_lists=True.

Returns

The last tree in this tree sequence.

Return type
ltrim(record_provenance=True)[source]

Returns a copy of this tree sequence with a potentially changed coordinate system, such that empty regions (i.e., those not covered by any edge) at the start of the tree sequence are trimmed away, and the leftmost edge starts at position 0. This affects the reported position of sites and edges. Additionally, sites and their associated mutations to the left of the new zero point are thrown away.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

property max_root_time

Returns the time of the oldest root in any of the trees in this tree sequence. This is usually equal to np.max(ts.tables.nodes.time) but may not be since there can be non-sample nodes that are not present in any tree. Note that isolated samples are also defined as roots (so there can be a max_root_time even in a tree sequence with no edges).

Returns

The maximum time of a root in this tree sequence.

Return type

float

Raises

ValueError – If there are no samples in the tree, and hence no roots (as roots are defined by the ends of the upward paths from the set of samples).

mean_descendants(sample_sets)[source]

Computes for every node the mean number of samples in each of the sample_sets that descend from that node, averaged over the portions of the genome for which the node is ancestral to any sample. The output is an array, C[node, j], which reports the total span of all genomes in sample_sets[j] that inherit from node, divided by the total span of the genome on which node is an ancestor to any sample in the tree sequence.

Warning

The interface for this method is preliminary and may be subject to backwards incompatible changes in the near future. The long-term stable API for this method will be consistent with other Statistics. In particular, the normalization by proportion of the genome that node is an ancestor to anyone may not be the default behaviour in the future.

Parameters

sample_sets (list) – A list of lists of node IDs.

Returns

An array with dimensions (number of nodes in the tree sequence, number of reference sets)

property metadata

The decoded metadata for this TreeSequence.

property metadata_schema

The tskit.MetadataSchema for this TreeSequence.

migration(id_)[source]

Returns the migration in this tree sequence with the specified ID.

Return type

Migration

migrations()[source]

Returns an iterable sequence of all the migrations in this tree sequence.

Migrations are returned in nondecreasing order of the time value.

Returns

An iterable sequence of all migrations.

Return type

Sequence(Migration)

mutation(id_)[source]

Returns the mutation in this tree sequence with the specified ID.

Return type

Mutation

mutations()[source]

Returns an iterator over all the mutations in this tree sequence. Mutations are returned in order of nondecreasing site ID. See the Mutation class for details on the available fields for each mutation.

The returned iterator is equivalent to iterating over all sites and all mutations in each site, i.e.:

>>> for site in tree_sequence.sites():
>>>     for mutation in site.mutations:
>>>         yield mutation

Returns

An iterator over all mutations in this tree sequence.

Return type

iter(Mutation)

property nbytes

Returns the total number of bytes required to store the data in this tree sequence. Note that this may not be equal to the actual memory footprint.

node(id_)[source]

Returns the node in this tree sequence with the specified ID.

Return type

Node

nodes()[source]

Returns an iterable sequence of all the nodes in this tree sequence.

Returns

An iterable sequence of all nodes.

Return type

Sequence(Node)

property num_edges

Returns the number of edges in this tree sequence.

Returns

The number of edges in this tree sequence.

Return type

int

property num_individuals

Returns the number of individuals in this tree sequence.

Returns

The number of individuals in this tree sequence.

Return type

int

property num_migrations

Returns the number of migrations in this tree sequence.

Returns

The number of migrations in this tree sequence.

Return type

int

property num_mutations

Returns the number of mutations in this tree sequence.

Returns

The number of mutations in this tree sequence.

Return type

int

property num_nodes

Returns the number of nodes in this tree sequence.

Returns

The number of nodes in this tree sequence.

Return type

int

property num_populations

Returns the number of populations in this tree sequence.

Returns

The number of populations in this tree sequence.

Return type

int

property num_provenances

Returns the number of provenances in this tree sequence.

Returns

The number of provenances in this tree sequence.

Return type

int

property num_samples

Returns the number of samples in this tree sequence. This is the number of sample nodes in each tree.

Returns

The number of sample nodes in this tree sequence.

Return type

int

property num_sites

Returns the number of sites in this tree sequence.

Returns

The number of sites in this tree sequence.

Return type

int

property num_trees

Returns the number of distinct trees in this tree sequence. This is equal to the number of trees returned by the trees() method.

Returns

The number of trees in this tree sequence.

Return type

int

pairwise_diversity(samples=None)[source]

Returns the pairwise nucleotide site diversity, the average number of sites that differ between a randomly chosen pair of samples. If samples is specified, calculate the diversity within this set.

Deprecated since version 0.2.0: please use diversity() instead. Since version 0.2.0 the error semantics have also changed slightly. It is no longer an error when there is one sample and a tskit.LibraryError is raised when non-sample IDs are provided rather than a ValueError. It is also no longer an error to compute pairwise diversity at sites with multiple mutations.

Parameters

samples (list) – The set of samples within which we calculate the diversity. If None, calculate diversity within the entire sample.

Returns

The pairwise nucleotide site diversity.

Return type

float

population(id_)[source]

Returns the population in this tree sequence with the specified ID.

Return type

Population

populations()[source]

Returns an iterable sequence of all the populations in this tree sequence.

Returns

An iterable sequence of all populations.

Return type

Sequence(Population)

provenances()[source]

Returns an iterable sequence of all the provenances in this tree sequence.

Returns

An iterable sequence of all provenances.

Return type

Sequence(Provenance)

rtrim(record_provenance=True)[source]

Returns a copy of this tree sequence with the sequence_length property reset so that the sequence ends at the end of the rightmost edge. Additionally, sites and their associated mutations at positions greater than the new sequence_length are thrown away.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

sample_count_stat(sample_sets, f, output_dim, windows=None, polarised=False, mode=None, span_normalise=True, strict=True)[source]

Compute a windowed statistic from sample counts and a summary function. This is a wrapper around general_stat() for the common case in which the weights are all either 1 or 0, i.e., functions of the joint allele frequency spectrum. See the statistics interface section for details on sample sets, windows, mode, span normalise, and return value. If sample_sets is a list of k sets of samples, then f should be a function that takes an argument of length k and returns a one-dimensional array. The j-th element of the argument to f will be the number of samples in sample_sets[j] that lie below the node that f is being evaluated for. See general_stat() for more details.

Here is a contrived example: suppose that A and B are two sets of samples with nA and nB elements, respectively. Passing these as sample sets will give f an argument of length two, giving the number of samples in A and B below the node in question. So, if we define

def f(x):
pA = x[0] / nA
pB = x[1] / nB
return np.array([pA * pB])


then if all sites are biallelic,

ts.sample_count_stat([A, B], f, 1, windows="sites", polarised=False, mode="site")


would compute, for each site, the product of the derived allele frequencies in the two sample sets, in a (num sites, 1) array. If instead f returns np.array([pA, pB, pA * pB]), then the output would be a (num sites, 3) array, with the first two columns giving the allele frequencies in A and B, respectively.

Note

The summary function f should return zero when given both 0 and the sample size (i.e., f(0) = 0 and f(np.array([len(x) for x in sample_sets])) = 0). This is necessary for the statistic to be unaffected by parts of the tree sequence ancestral to none or all of the samples, respectively.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• f – A function that takes a one-dimensional array of length equal to the number of sample sets and returns a one-dimensional array.

• output_dim (int) – The length of f’s return value.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• polarised (bool) – Whether to leave the ancestral state out of computations: see Statistics for more details.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

• strict (bool) – Whether to check that f(0) and f(total weight) are zero.

Returns

A ndarray with shape equal to (num windows, num statistics).

samples(population=None, population_id=None)[source]

Returns an array of the sample node IDs in this tree sequence. If the population parameter is specified, only return sample IDs from that population.

Parameters
• population (int) – The population of interest. If None, return all samples.

• population_id (int) – Deprecated alias for population.

Returns

A numpy array of the node IDs for the samples of interest, listed in numerical order.

Return type

numpy.ndarray (dtype=np.int32)

segregating_sites(sample_sets=None, windows=None, mode='site', span_normalise=True)[source]

Computes the density of segregating sites for each of the sets of nodes from sample_sets, and related quantities. Please see the one-way statistics section for details on how the sample_sets argument is interpreted and how it interacts with the dimensions of the output array. See the statistics interface section for details on windows, mode, span normalise, and return value.

What is computed depends on mode. For a sample set A, computes:

“site”

The sum over sites of the number of alleles found in A at each site minus one, per unit of chromosome length. If all sites have at most two alleles, this is the density of sites that are polymorphic in A. To get the number of segregating minor alleles per window, pass span_normalise=False.

“branch”

The total length of all branches in the tree subtended by the samples in A, averaged across the window.

“node”

The proportion of the window on which the node is ancestral to some, but not all, of the samples in A.

Parameters
• sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

property sequence_length

Returns the sequence length in this tree sequence. This defines the genomic scale over which tree coordinates are defined. Given a tree sequence with a sequence length $$L$$, the constituent trees will be defined over the half-closed interval $$[0, L)$$. Each tree then covers some subset of this interval — see tskit.Tree.interval for details.

Returns

The length of the sequence in this tree sequence in bases.

Return type

float

simplify(samples=None, *, map_nodes=False, reduce_to_site_topology=False, filter_populations=True, filter_individuals=True, filter_sites=True, keep_unary=False, keep_unary_in_individuals=None, keep_input_roots=False, record_provenance=True, filter_zero_mutation_sites=None)[source]

Returns a simplified tree sequence that retains only the history of the nodes given in the list samples. If map_nodes is true, also return a numpy array whose uth element is the ID of the node in the simplified tree sequence that corresponds to node u in the original tree sequence, or tskit.NULL (-1) if u is no longer present in the simplified tree sequence.

In the returned tree sequence, the node with ID 0 corresponds to samples[0], node 1 corresponds to samples[1] etc., and all the passed-in nodes are flagged as samples. The remaining node IDs in the returned tree sequence are allocated sequentially in time order and are not flagged as samples.

If you wish to simplify a set of tables that do not satisfy all requirements for building a TreeSequence, then use TableCollection.simplify().

If the reduce_to_site_topology parameter is True, the returned tree sequence will contain only topological information that is necessary to represent the trees that contain sites. If there are zero sites in this tree sequence, this will result in an output tree sequence with zero edges. When the number of sites is greater than zero, every tree in the output tree sequence will contain at least one site. For a given site, the topology of the tree containing that site will be identical (up to node ID remapping) to the topology of the corresponding tree in the input tree sequence.

If filter_populations, filter_individuals or filter_sites is True, any of the corresponding objects that are not referenced elsewhere are filtered out. As this is the default behaviour, it is important to realise IDs for these objects may change through simplification. By setting these parameters to False, however, the corresponding tables can be preserved without changes.

Parameters
• samples (list[int]) – A list of node IDs to retain as samples. They need not be nodes marked as samples in the original tree sequence, but will constitute the entire set of samples in the returned tree sequence. If not specified or None, use all nodes marked with the IS_SAMPLE flag. The list may be provided as a numpy array (or array-like) object (dtype=np.int32).

• map_nodes (bool) – If True, return a tuple containing the resulting tree sequence and a numpy array mapping node IDs in the current tree sequence to their corresponding node IDs in the returned tree sequence. If False (the default), return only the tree sequence object itself.

• reduce_to_site_topology (bool) – Whether to reduce the topology down to the trees that are present at sites. (Default: False)

• filter_populations (bool) – If True, remove any populations that are not referenced by nodes after simplification; new population IDs are allocated sequentially from zero. If False, the population table will not be altered in any way. (Default: True)

• filter_individuals (bool) – If True, remove any individuals that are not referenced by nodes after simplification; new individual IDs are allocated sequentially from zero. If False, the individual table will not be altered in any way. (Default: True)

• filter_sites (bool) – If True, remove any sites that are not referenced by mutations after simplification; new site IDs are allocated sequentially from zero. If False, the site table will not be altered in any way. (Default: True)

• keep_unary (bool) – If True, preserve unary nodes (i.e., nodes with exactly one child) that exist on the path from samples to root. (Default: False)

• keep_unary_in_individuals (bool) – If True, preserve unary nodes that exist on the path from samples to root, but only if they are associated with an individual in the individuals table. Cannot be specified at the same time as keep_unary. (Default: None, equivalent to False)

• keep_input_roots (bool) – Whether to retain history ancestral to the MRCA of the samples. If False, no topology older than the MRCAs of the samples will be included. If True the roots of all trees in the returned tree sequence will be the same roots as in the original tree sequence. (Default: False)

• record_provenance (bool) – If True, record details of this call to simplify in the returned tree sequence’s provenance information (Default: True).

• filter_zero_mutation_sites (bool) – Deprecated alias for filter_sites.

Returns

The simplified tree sequence, or (if map_nodes is True) a tuple consisting of the simplified tree sequence and a numpy array mapping source node IDs to their corresponding IDs in the new tree sequence.

Return type
site(id_)[source]

Returns the site in this tree sequence with the specified ID.

Return type

Site

sites()[source]

Returns an iterable sequence of all the sites in this tree sequence. Sites are returned in order of increasing ID (and also position). See the Site class for details on the available fields for each site.

Returns

An iterable sequence of all sites.

Return type

Sequence(Site)

subset(nodes, record_provenance=True, reorder_populations=True, remove_unreferenced=True)[source]

Returns a tree sequence containing only information directly referencing the provided list of nodes to retain. The result will retain only the nodes whose IDs are listed in nodes, only edges for which both parent and child are in nodes, only mutations whose node is in nodes, and only individuals that are referred to by one of the retained nodes. Note that this does not retain the ancestry of these nodes - for that, see simplify().

This has the side effect of reordering the nodes, individuals, and populations in the tree sequence: the nodes in the new tree sequence will be in the order provided in nodes, and both individuals and populations will be ordered by the earliest retained node that refers to them. (However, reorder_populations may be set to False to keep the population table unchanged.)

By default, the method removes all individuals and populations not referenced by any nodes, and all sites not referenced by any mutations. To retain these unreferenced individuals, populations, and sites, pass remove_unreferenced=False. If this is done, the site table will remain unchanged, unreferenced individuals will appear at the end of the individuals table (and in their original order), and unreferenced populations will appear at the end of the population table (unless reorder_populations=False).

keep_intervals() for subsetting a given portion of the genome; simplify() for retaining the ancestry of a subset of nodes.

Parameters
• nodes (list) – The list of nodes for which to retain information. This may be a numpy array (or array-like) object (dtype=np.int32).

• record_provenance (bool) – Whether to record a provenance entry in the provenance table for this operation.

• reorder_populations (bool) – Whether to reorder populations (default: True). If False, the population table will not be altered in any way.

• remove_unreferenced (bool) – Whether sites, individuals, and populations that are not referred to by any retained entries in the tables should be removed (default: True). See the description for details.

Return type

TreeSequence

property table_metadata_schemas

The set of metadata schemas for the tables in this tree sequence.

property tables

A copy of the tables underlying this tree sequence. See also dump_tables().

Warning

This property currently returns a copy of the tables underlying a tree sequence but it may return a read-only view in the future. Thus, if the tables will subsequently be updated, please use the dump_tables() method instead as this will always return a new copy of the TableCollection.

Returns

A TableCollection containing all a copy of the tables underlying this tree sequence.

Return type

TableCollection

property tables_dict

Returns a dictionary mapping names to tables in the underlying TableCollection. Equivalent to calling ts.tables.name_map.

to_macs()[source]

Return a macs encoding of this tree sequence.

Returns

The macs representation of this TreeSequence as a string.

Return type

str

to_nexus(precision=14)[source]

Returns a nexus encoding of this tree sequence. Trees along the sequence are listed sequentially in the TREES block. The tree spanning the interval $$[x, y)$$ is given the name “tree_x_y”. Spatial positions are written at the specified precision.

Nodes in the tree sequence are identified by the taxon labels of the form f"tsk_{node.id}_{node.flags}", such that a node with id=5 and flags=1 will have the label "tsk_5_1" (please see the data model section for details on the interpretation of node ID and flags values). These labels are listed for all nodes in the tree sequence in the TAXLABELS block.

Parameters

precision (int) – The numerical precision with which branch lengths and tree positions are printed.

Returns

A nexus representation of this TreeSequence.

Return type

str

trait_correlation(W, windows=None, mode='site', span_normalise=True)[source]

Computes the mean squared correlations between each of the columns of W (the “phenotypes”) and inheritance along the tree sequence. See the statistics interface section for details on windows, mode, span normalise, and return value. Operates on all samples in the tree sequence.

This is computed as squared covariance in trait_covariance, but divided by $$p (1-p)$$, where p is the proportion of samples inheriting from the allele, branch, or node in question.

What is computed depends on mode:

“site”

The sum of squared correlations between presence/absence of each allele and phenotypes, divided by length of the window (if span_normalise=True). This is computed as the trait_covariance divided by the variance of the relevant column of W and by ;math:p * (1 - p), where $$p$$ is the allele frequency.

“branch”

The sum of squared correlations between the split induced by each branch and phenotypes, multiplied by branch length, averaged across trees in the window. This is computed as the trait_covariance, divided by the variance of the column of w and by $$p * (1 - p)$$, where $$p$$ is the proportion of the samples lying below the branch.

“node”

For each node, the squared correlation between the property of inheriting from this node and phenotypes, computed as in “branch”.

Note that above we divide by the sample variance, which for a vector x of length n is np.var(x) * n / (n-1).

Parameters
• W (numpy.ndarray) – An array of values with one row for each sample and one column for each “phenotype”. Each column must have positive standard deviation.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

trait_covariance(W, windows=None, mode='site', span_normalise=True)[source]

Computes the mean squared covariances between each of the columns of W (the “phenotypes”) and inheritance along the tree sequence. See the statistics interface section for details on windows, mode, span normalise, and return value. Operates on all samples in the tree sequence.

Concretely, if g is a binary vector that indicates inheritance from an allele, branch, or node and w is a column of W, normalised to have mean zero, then the covariance of g and w is $$\sum_i g_i w_i$$, the sum of the weights corresponding to entries of g that are 1. Since weights sum to zero, this is also equal to the sum of weights whose entries of g are 0. So, $$cov(g,w)^2 = ((\sum_i g_i w_i)^2 + (\sum_i (1-g_i) w_i)^2)/2$$.

What is computed depends on mode:

“site”

The sum of squared covariances between presence/absence of each allele and phenotypes, divided by length of the window (if span_normalise=True). This is computed as sum_a (sum(w[a])^2 / 2), where w is a column of W with the average subtracted off, and w[a] is the sum of all entries of w corresponding to samples carrying allele “a”, and the first sum is over all alleles.

“branch”

The sum of squared covariances between the split induced by each branch and phenotypes, multiplied by branch length, averaged across trees in the window. This is computed as above: a branch with total weight w[b] below b contributes (branch length) * w[b]^2 to the total value for a tree. (Since the sum of w is zero, the total weight below b and not below b are equal, canceling the factor of 2 above.)

“node”

For each node, the squared covariance between the property of inheriting from this node and phenotypes, computed as in “branch”.

Parameters
• W (numpy.ndarray) – An array of values with one row for each sample and one column for each “phenotype”.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

trait_linear_model(W, Z=None, windows=None, mode='site', span_normalise=True)[source]

Finds the relationship between trait and genotype after accounting for covariates. Concretely, for each trait w (i.e., each column of W), this does a least-squares fit of the linear model $$w \sim g + Z$$, where $$g$$ is inheritance in the tree sequence (e.g., genotype) and the columns of $$Z$$ are covariates, and returns the squared coefficient of $$g$$ in this linear model. See the statistics interface section for details on windows, mode, span normalise, and return value. Operates on all samples in the tree sequence.

To do this, if g is a binary vector that indicates inheritance from an allele, branch, or node and w is a column of W, there are $$k$$ columns of $$Z$$, and the $$k+2$$-vector $$b$$ minimises $$\sum_i (w_i - b_0 - b_1 g_i - b_2 z_{2,i} - ... b_{k+2} z_{k+2,i})^2$$ then this returns the number $$b_1^2$$. If $$g$$ lies in the linear span of the columns of $$Z$$, then $$b_1$$ is set to 0. To fit the linear model without covariates (only the intercept), set Z = None.

What is computed depends on mode:

“site”

Computes the sum of $$b_1^2/2$$ for each allele in the window, as above with $$g$$ indicating presence/absence of the allele, then divided by the length of the window if span_normalise=True. (For biallelic loci, this number is the same for both alleles, and so summing over each cancels the factor of two.)

“branch”

The squared coefficient b_1^2, computed for the split induced by each branch (i.e., with $$g$$ indicating inheritance from that branch), multiplied by branch length and tree span, summed over all trees in the window, and divided by the length of the window if span_normalise=True.

“node”

For each node, the squared coefficient b_1^2, computed for the property of inheriting from this node, as in “branch”.

Parameters
• W (numpy.ndarray) – An array of values with one row for each sample and one column for each “phenotype”.

• Z (numpy.ndarray) – An array of values with one row for each sample and one column for each “covariate”, or None. Columns of Z must be linearly independent.

• windows (list) – An increasing list of breakpoints between the windows to compute the statistic in.

• mode (str) – A string giving the “type” of the statistic to be computed (defaults to “site”).

• span_normalise (bool) – Whether to divide the result by the span of the window (defaults to True).

Returns

A ndarray with shape equal to (num windows, num statistics).

trait_regression(*args, **kwargs)[source]

Deprecated synonym for trait_linear_model.

trees(tracked_samples=None, *, sample_lists=False, root_threshold=1, sample_counts=None, tracked_leaves=None, leaf_counts=None, leaf_lists=None)[source]

Returns an iterator over the trees in this tree sequence. Each value returned in this iterator is an instance of Tree. Upon successful termination of the iterator, the tree will be in the “cleared” null state.

The sample_lists and tracked_samples parameters are passed to the Tree constructor, and control the options that are set in the returned tree instance.

Warning

Do not store the results of this iterator in a list! For performance reasons, the same underlying object is used for every tree returned which will most likely lead to unexpected behaviour. If you wish to obtain a list of trees in a tree sequence please use ts.aslist() instead.

Parameters
• tracked_samples (list) – The list of samples to be tracked and counted using the Tree.num_tracked_samples() method.

• sample_lists (bool) – If True, provide more efficient access to the samples beneath a given node using the Tree.samples() method.

• root_threshold (int) – The minimum number of samples that a node must be ancestral to for it to be in the list of roots. By default this is 1, so that isolated samples (representing missing data) are roots. To efficiently restrict the roots of the tree to those subtending meaningful topology, set this to 2. This value is only relevant when trees have multiple roots.

• sample_counts (bool) – Deprecated since 0.2.4.

Returns

An iterator over the Trees in this tree sequence.

Return type

collections.abc.Iterable, Tree

trim(record_provenance=True)[source]

Returns a copy of this tree sequence with any empty regions (i.e., those not covered by any edge) on the right and left trimmed away. This may reset both the coordinate system and the sequence_length property. It is functionally equivalent to rtrim() followed by ltrim(). Sites and their associated mutations in the empty regions are thrown away.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

union(other, node_mapping, check_shared_equality=True, add_populations=True, record_provenance=True)[source]

Returns an expanded tree sequence which contains the node-wise union of self and other, obtained by adding the non-shared portions of other onto self. The “shared” portions are specified using a map that specifies which nodes in other are equivalent to those in self: the node_mapping argument should be an array of length equal to the number of nodes in other and whose entries are the ID of the matching node in self, or tskit.NULL if there is no matching node. Those nodes in other that map to tskit.NULL will be added to self, along with:

1. Individuals whose nodes are new to self.

2. Edges whose parent or child are new to self.

3. Mutations whose nodes are new to self.

4. Sites which were not present in self, if the site contains a newly added mutation.

By default, populations of newly added nodes are assumed to be new populations, and added to the population table as well.

Note that this operation also sorts the resulting tables, so the resulting tree sequence may not be equal to self even if nothing new was added (although it would differ only in ordering of the tables).

Parameters
• other (TableCollection) – Another table collection.

• node_mapping (list) – An array of node IDs that relate nodes in other to nodes in self.

• check_shared_equality (bool) – If True, the shared portions of the tree sequences will be checked for equality. It does so by subsetting both self and other on the equivalent nodes specified in node_mapping, and then checking for equality of the subsets.

• add_populations (bool) – If True, nodes new to self will be assigned new population IDs.

• record_provenance (bool) – Whether to record a provenance entry in the provenance table for this operation.

variants(*, as_bytes=False, samples=None, isolated_as_missing=None, alleles=None, impute_missing_data=None)[source]

Returns an iterator over the variants in this tree sequence. See the Variant class for details on the fields of each returned object. The genotypes for the variants are numpy arrays, corresponding to indexes into the alleles attribute in the Variant object. By default, the alleles for each site are generated automatically, such that the ancestral state is at the zeroth index and subsequent alleles are listed in no particular order. This means that the encoding of alleles in terms of genotype values can vary from site-to-site, which is sometimes inconvenient. It is possible to specify a fixed mapping from allele strings to genotype values using the alleles parameter. For example, if we set alleles=("A", "C", "G", "T"), this will map allele “A” to 0, “C” to 1 and so on (the ALLELES_ACGT constant provides a shortcut for this common mapping).

By default, genotypes are generated for all samples. The samples parameter allows us to specify the nodes for which genotypes are generated; output order of genotypes in the returned variants corresponds to the order of the samples in this list. It is also possible to provide non-sample nodes as an argument here, if you wish to generate genotypes for (e.g.) internal nodes. However, isolated_as_missing must be False in this case, as it is not possible to detect missing data for non-sample nodes.

If isolated samples are present at a given site without mutations above them, they are interpreted by default as missing data, and the genotypes array will contain a special value MISSING_DATA (-1) to identify them while the alleles tuple will end with the value None (note that this will be the case whether or not we specify a fixed mapping using the alleles parameter; see the Variant class for more details). Alternatively, if isolated_as_missing is set to to False, such isolated samples will not be treated as missing, and instead assigned the ancestral state (this was the default behaviour in versions prior to 0.2.0). Prior to 0.3.0 the impute_missing_data argument controlled this behaviour.

Note

The as_bytes parameter is kept as a compatibility option for older code. It is not the recommended way of accessing variant data, and will be deprecated in a later release.

Parameters
• as_bytes (bool) – If True, the genotype values will be returned as a Python bytes object. Legacy use only.

• samples (array_like) – An array of node IDs for which to generate genotypes, or None for all sample nodes. Default: None.

• isolated_as_missing (bool) – If True, the allele assigned to missing samples (i.e., isolated samples without mutations) is the missing_data_character. If False, missing samples will be assigned the ancestral state. Default: True.

• alleles (tuple) – A tuple of strings defining the encoding of alleles as integer genotype values. At least one allele must be provided. If duplicate alleles are provided, output genotypes will always be encoded as the first occurrence of the allele. If None (the default), the alleles are encoded as they are encountered during genotype generation.

• impute_missing_data (bool) – Deprecated in 0.3.0. Use isolated_as_missing, but inverting value. Will be removed in a future version

Returns

An iterator of all variants this tree sequence.

Return type

iter(Variant)

write_vcf(output, ploidy=None, contig_id='1', individuals=None, individual_names=None, position_transform=None)[source]

Writes a VCF formatted file to the specified file-like object. If there is individual information present in the tree sequence (see Individual Table), the values for sample nodes associated with these individuals are combined into phased multiploid individuals and output.

If there is no individual data present in the tree sequence, synthetic individuals are created by combining adjacent samples, and the number of samples combined is equal to the specified ploidy value (1 by default). For example, if we have a ploidy of 2 and a sample of size 6, then we will have 3 diploid samples in the output, consisting of the combined genotypes for samples [0, 1], [2, 3] and [4, 5]. If we had genotypes 011110 at a particular variant, then we would output the diploid genotypes 0|1, 1|1 and 1|0 in VCF.

Each individual in the output is identified by a string; these are the VCF “sample” names. By default, these are of the form tsk_0, tsk_1 etc, up to the number of individuals, but can be manually specified using the individual_names argument. We do not check for duplicates in this array, or perform any checks to ensure that the output VCF is well-formed.

Note

Warning to plink users:

As the default first individual name is tsk_0, plink will throw this error when loading the VCF:

Error: Sample ID ends with "_0", which induces an invalid IID of '0'.

This can be fixed by using the individual_names argument to set the names to anything where the first name doesn’t end with _0. An example implementation for diploid individuals is:

n_dip_indv = int(ts.num_samples / 2)
indv_names = [f"tsk_{str(i)}indv" for i in range(n_dip_indv)]
with open("output.vcf", "w") as vcf_file:
ts.write_vcf(vcf_file, ploidy=2, individual_names=indv_names)


Adding a second _ (eg: tsk_0_indv) is not recommended as plink uses _ as the default separator for separating family id and individual id, and two _ will throw an error.

The REF value in the output VCF is the ancestral allele for a site and ALT values are the remaining alleles. It is important to note, therefore, that for real data this means that the REF value for a given site may not be equal to the reference allele. We also do not check that the alleles result in a valid VCF—for example, it is possible to use the tab character as an allele, leading to a broken VCF.

The position_transform argument provides a way to flexibly translate the genomic location of sites in tskit to the appropriate value in VCF. There are two fundamental differences in the way that tskit and VCF define genomic coordinates. The first is that tskit uses floating point values to encode positions, whereas VCF uses integers. Thus, if the tree sequence contains positions at non-integral locations there is an information loss incurred by translating to VCF. By default, we round the site positions to the nearest integer, such that there may be several sites with the same integer position in the output. The second difference between VCF and tskit is that VCF is defined to be a 1-based coordinate system, whereas tskit uses 0-based. However, how coordinates are transformed depends on the VCF parser, and so we do not account for this change in coordinate system by default.

Example usage:

with open("output.vcf", "w") as vcf_file:
tree_sequence.write_vcf(vcf_file, ploidy=2)


The VCF output can also be compressed using the gzip module, if you wish:

import gzip

with gzip.open("output.vcf.gz", "wt") as f:
ts.write_vcf(f)


However, this gzipped VCF may not be fully compatible with downstream tools such as tabix, which may require the VCF use the specialised bgzip format. A general way to convert VCF data to various formats is to pipe the text produced by tskit into bcftools, as done here:

import os
import subprocess

write_pipe = os.fdopen(write_fd, "w")
with open("output.bcf", "w") as bcf_file:
proc = subprocess.Popen(
["bcftools", "view", "-O", "b"], stdin=read_fd, stdout=bcf_file
)
ts.write_vcf(write_pipe)
write_pipe.close()
proc.wait()
if proc.returncode != 0:
raise RuntimeError("bcftools failed with status:", proc.returncode)


This can also be achieved on the command line use the tskit vcf command, e.g.:

\$ tskit vcf example.trees | bcftools view -O b > example.bcf

Parameters
• output (io.IOBase) – The file-like object to write the VCF output.

• ploidy (int) – The ploidy of the individuals to be written to VCF. This sample size must be evenly divisible by ploidy.

• contig_id (str) – The value of the CHROM column in the output VCF.

• individuals (list(int)) – A list containing the individual IDs to write out to VCF. Defaults to all individuals in the tree sequence.

• individual_names (list(str)) – A list of string names to identify individual columns in the VCF. In VCF nomenclature, these are the sample IDs. If specified, this must be a list of strings of length equal to the number of individuals to be output. Note that we do not check the form of these strings in any way, so that is is possible to output malformed VCF (for example, by embedding a tab character within on of the names). The default is to output tsk_j for the jth individual.

• position_transform – A callable that transforms the site position values into integer valued coordinates suitable for VCF. The function takes a single positional parameter x and must return an integer numpy array the same dimension as x. By default, this is set to numpy.round() which will round values to the nearest integer. If the string “legacy” is provided here, the pre 0.2.0 legacy behaviour of rounding values to the nearest integer (starting from 1) and avoiding the output of identical positions by incrementing is used.

### The Tree class¶

Trees in a tree sequence can be obtained by iterating over TreeSequence.trees() and specific trees can be accessed using methods such as TreeSequence.first(), TreeSequence.at() and TreeSequence.at_index(). Each tree is an instance of the following class which provides methods, for example, to access information about particular nodes in the tree.

class tskit.Tree[source]

A single tree in a TreeSequence. Please see the Processing trees section for information on how efficiently access trees sequentially or obtain a list of individual trees in a tree sequence.

The sample_lists parameter controls the features that are enabled for this tree. If sample_lists is True a more efficient algorithm is used in the Tree.samples() method.

The tracked_samples parameter can be used to efficiently count the number of samples in a given set that exist in a particular subtree using the Tree.num_tracked_samples() method.

The Tree class is a state-machine which has a state corresponding to each of the trees in the parent tree sequence. We transition between these states by using the seek functions like Tree.first(), Tree.last(), Tree.seek() and Tree.seek_index(). There is one more state, the so-called “null” or “cleared” state. This is the state that a Tree is in immediately after initialisation; it has an index of -1, and no edges. We can also enter the null state by calling Tree.next() on the last tree in a sequence, calling Tree.prev() on the first tree in a sequence or calling calling the Tree.clear() method at any time.

The high-level TreeSequence seeking and iterations methods (e.g, TreeSequence.trees()) are built on these low-level state-machine seek operations. We recommend these higher level operations for most users.

Parameters
• tree_sequence (TreeSequence) – The parent tree sequence.

• tracked_samples (list) – The list of samples to be tracked and counted using the Tree.num_tracked_samples() method.

• sample_lists (bool) – If True, provide more efficient access to the samples beneath a give node using the Tree.samples() method.

• root_threshold (int) – The minimum number of samples that a node must be ancestral to for it to be in the list of roots. By default this is 1, so that isolated samples (representing missing data) are roots. To efficiently restrict the roots of the tree to those subtending meaningful topology, set this to 2. This value is only relevant when trees have multiple roots.

• sample_counts (bool) – Deprecated since 0.2.4.

Methods

 Convert tree to dict of dicts for conversion to a networkx graph. Returns the length of the branch (in units of time) joining the specified node to its parent. Returns the children of the specified node u as a tuple of integer node IDs. Resets this tree back to the initial null state. Returns a deep copy of this tree. count_topologies([sample_sets]) Calculates the distribution of embedded topologies for every combination of the sample sets in sample_sets. Returns the number of nodes on the path from u to a root, not including u. draw([path, width, height, node_labels, …]) Returns a drawing of this tree. draw_svg([path, size, time_scale, …]) Return an SVG representation of a single tree. draw_text([orientation, node_labels, …]) Create a text representation of a tree. Seeks to the first tree in the sequence. generate_balanced(num_leaves, *[, arity, …]) Generate a Tree with the specified number of leaves that is maximally balanced. generate_comb(num_leaves, *[, span, …]) Generate a Tree in which all internal nodes have two children and the left child is a leaf. generate_random_binary(num_leaves, *[, …]) Generate a random binary Tree with $$n$$ = num_leaves leaves with an equal probability of returning any topology and leaf label permutation among the $$(2n - 3)! / (2^{n - 2} (n - 2)!)$$ leaf-labelled binary trees. generate_star(num_leaves, *[, span, …]) Generate a Tree whose leaf nodes all have the same parent (i.e., a “star” tree). is_descendant(u, v) Returns True if the specified node u is a descendant of node v and False otherwise. Returns True if the specified node is not a leaf. Returns True if the specified node is isolated in this tree: that is it has no parents and no children. Returns True if the specified node is a leaf. Returns True if the specified node is a sample. kc_distance(other[, lambda_]) Returns the Kendall-Colijn distance between the specified pair of trees. Seeks to the last tree in the sequence. leaves([u]) Returns an iterator over all the leaves in this tree that are underneath the specified node. Returns the leftmost child of the specified node. Returns the sibling node to the left of u, or tskit.NULL if u does not have a left sibling. map_mutations(genotypes, alleles[, …]) Given observations for the samples in this tree described by the specified set of genotypes and alleles, return a parsimonious set of state transitions explaining these observations. mrca(u, v) Returns the most recent common ancestor of the specified nodes. Returns an iterator over all the mutations in this tree. newick([precision, root, node_labels, …]) Returns a newick encoding of this tree. Seeks to the next tree in the sequence. nodes([root, order]) Returns an iterator over the node IDs reachable from the root(s) in this tree. Returns the number of children of the specified Returns the number of samples in this tree underneath the specified node (including the node itself). Returns the number of samples in the set specified in the tracked_samples parameter of the TreeSequence.trees() method underneath the specified node. Returns the parent of the specified node. Returns the population associated with the specified node. Seeks to the previous tree in the sequence. Produce the rank of this tree in the enumeration of all leaf-labelled trees of n leaves. Returns the rightmost child of the specified node. Returns the sibling node to the right of u, or tskit.NULL if u does not have a right sibling. samples([u]) Returns an iterator over the numerical IDs of all the sample nodes in this tree that are underneath node u. seek(position) Sets the state to represent the tree that covers the specified position in the parent tree sequence. seek_index(index) Sets the state to represent the tree at the specified index in the parent tree sequence. Returns an iterator over all the sites in this tree. split_polytomies(*[, epsilon, method, …]) Return a new Tree where extra nodes and edges have been inserted so that any any node u with greater than 2 children — a multifurcation or “polytomy” — is resolved into successive bifurcations. Returns the time of the specified node. tmrca(u, v) Returns the time of the most recent common ancestor of the specified nodes. unrank(num_leaves, rank, *[, span, …]) Reconstruct the tree of the given rank (see tskit.Tree.rank()) with num_leaves leaves.

Attributes

 has_multiple_roots True if this tree has more than one root, False otherwise. has_single_root True if this tree has a single root, False otherwise. index Returns the index this tree occupies in the parent tree sequence. interval Returns the coordinates of the genomic interval that this tree represents the history of. left_child_array A numpy array (dtype=np.int32) encoding the left child of each node in this tree, such that tree.left_child_array[u] == tree.left_child(u) for all 0 <= u < ts.num_nodes. left_root The leftmost root in this tree. left_sib_array A numpy array (dtype=np.int32) encoding the left sib of each node in this tree, such that tree.left_sib_array[u] == tree.left_sib(u) for all 0 <= u < ts.num_nodes. num_mutations Returns the total number of mutations across all sites on this tree. num_nodes Returns the number of nodes in the TreeSequence this tree is in. num_roots The number of roots in this tree, as defined in the roots attribute. num_sites Returns the number of sites on this tree. parent_array A numpy array (dtype=np.int32) encoding the parent of each node in this tree, such that tree.parent_array[u] == tree.parent(u) for all 0 <= u < ts.num_nodes. right_child_array A numpy array (dtype=np.int32) encoding the right child of each node in this tree, such that tree.right_child_array[u] == tree.right_child(u) for all 0 <= u < ts.num_nodes. right_sib_array A numpy array (dtype=np.int32) encoding the right sib of each node in this tree, such that tree.right_sib_array[u] == tree.right_sib(u) for all 0 <= u < ts.num_nodes. root The root of this tree. root_threshold Returns the minimum number of samples that a node must be an ancestor of to be considered a potential root. roots The list of roots in this tree. sample_size Returns the sample size for this tree. span Returns the genomic distance that this tree spans. total_branch_length Returns the sum of all the branch lengths in this tree (in units of time). tree_sequence Returns the tree sequence that this tree is from.
as_dict_of_dicts()[source]

Convert tree to dict of dicts for conversion to a networkx graph.

For example:

>>> import networkx as nx
>>> nx.DiGraph(tree.as_dict_of_dicts())
>>> # undirected graphs work as well
>>> nx.Graph(tree.as_dict_of_dicts())

Returns

Dictionary of dictionaries of dictionaries where the first key is the source, the second key is the target of an edge, and the third key is an edge annotation. At this point the only annotation is “branch_length”, the length of the branch (in units of time).

branch_length(u)[source]

Returns the length of the branch (in units of time) joining the specified node to its parent. This is equivalent to

>>> tree.time(tree.parent(u)) - tree.time(u)


The branch length for a node that has no parent (e.g., a root) is defined as zero.

Note that this is not related to the property .length which is a deprecated alias for the genomic span covered by a tree.

Parameters

u (int) – The node of interest.

Returns

The branch length from u to its parent.

Return type

float

children(u)[source]

Returns the children of the specified node u as a tuple of integer node IDs. If u is a leaf, return the empty tuple. The ordering of children is arbitrary and should not be depended on; see the data model section for details.

Parameters

u (int) – The node of interest.

Returns

The children of u as a tuple of integers

Return type

tuple(int)

clear()[source]

Resets this tree back to the initial null state. Calling this method on a tree already in the null state has no effect.

copy()[source]

Returns a deep copy of this tree. The returned tree will have identical state to this tree.

Returns

A copy of this tree.

Return type

Tree

count_topologies(sample_sets=None)[source]

Calculates the distribution of embedded topologies for every combination of the sample sets in sample_sets. sample_sets defaults to all samples in the tree grouped by population.

sample_sets need not include all samples but must be pairwise disjoint.

The returned object is a tskit.TopologyCounter that contains counts of topologies per combination of sample sets. For example,

>>> topology_counter = tree.count_topologies()
>>> rank, count = topology_counter[0, 1, 2].most_common(1)[0]


produces the most common tree topology, with populations 0, 1 and 2 as its tips, according to the genealogies of those populations’ samples in this tree.

The counts for each topology in the tskit.TopologyCounter are absolute counts that we would get if we were to select all combinations of samples from the relevant sample sets. For sample sets $$[s_0, s_1, ..., s_n]$$, the total number of topologies for those sample sets is equal to $$|s_0| * |s_1| * ... * |s_n|$$, so the counts in the counter topology_counter[0, 1, ..., n] should sum to $$|s_0| * |s_1| * ... * |s_n|$$.

To convert the topology counts to probabilities, divide by the total possible number of sample combinations from the sample sets in question:

>>> set_sizes = [len(sample_set) for sample_set in sample_sets]
>>> p = count / (set_sizes[0] * set_sizes[1] * set_sizes[2])


Warning

The interface for this method is preliminary and may be subject to backwards incompatible changes in the near future.

Parameters

sample_sets (list) – A list of lists of Node IDs, specifying the groups of nodes to compute the statistic with. Defaults to all samples grouped by population.

Return type

tskit.TopologyCounter

Raises

ValueError – If nodes in sample_sets are invalid or are internal samples.

depth(u)[source]

Returns the number of nodes on the path from u to a root, not including u. Thus, the depth of a root is zero.

Parameters

u (int) – The node of interest.

Returns

The depth of u.

Return type

int

draw(path=None, width=None, height=None, node_labels=None, node_colours=None, mutation_labels=None, mutation_colours=None, format=None, edge_colours=None, time_scale=None, tree_height_scale=None, max_time=None, max_tree_height=None, order=None)[source]

Returns a drawing of this tree.

When working in a Jupyter notebook, use the IPython.display.SVG function to display the SVG output from this function inline in the notebook:

>>> SVG(tree.draw())


The unicode format uses unicode box drawing characters to render the tree. This allows rendered trees to be printed out to the terminal:

>>> print(tree.draw(format="unicode"))
6
┏━┻━┓
┃   5
┃ ┏━┻┓
┃ ┃  4
┃ ┃ ┏┻┓
3 0 1 2


The node_labels argument allows the user to specify custom labels for nodes, or no labels at all:

>>> print(tree.draw(format="unicode", node_labels={}))
┃
┏━┻━┓
┃   ┃
┃ ┏━┻┓
┃ ┃  ┃
┃ ┃ ┏┻┓
┃ ┃ ┃ ┃


Note: in some environments such as Jupyter notebooks with Windows or Mac, users have observed that the Unicode box drawings can be misaligned. In these cases, we recommend using the SVG or ASCII display formats instead. If you have a strong preference for aligned Unicode, you can try out the solution documented here.

Parameters
• path (str) – The path to the file to write the output. If None, do not write to file.

• width (int) – The width of the image in pixels. If not specified, either defaults to the minimum size required to depict the tree (text formats) or 200 pixels.

• height (int) – The height of the image in pixels. If not specified, either defaults to the minimum size required to depict the tree (text formats) or 200 pixels.

• node_labels (dict) – If specified, show custom labels for the nodes that are present in the map. Any nodes not specified in the map will not have a node label.

• node_colours (dict) – If specified, show custom colours for the nodes given in the map. Any nodes not specified in the map will take the default colour; a value of None is treated as transparent and hence the node symbol is not plotted. (Only supported in the SVG format.)

• mutation_labels (dict) – If specified, show custom labels for the mutations (specified by ID) that are present in the map. Any mutations not in the map will not have a label. (Showing mutations is currently only supported in the SVG format)

• mutation_colours (dict) – If specified, show custom colours for the mutations given in the map (specified by ID). As for node_colours, mutations not present in the map take the default colour, and those mapping to None are not drawn. (Only supported in the SVG format.)

• format (str) – The format of the returned image. Currently supported are ‘svg’, ‘ascii’ and ‘unicode’. Note that the Tree.draw_svg() method provides more comprehensive functionality for creating SVGs.

• edge_colours (dict) – If specified, show custom colours for the edge joining each node in the map to its parent. As for node_colours, unspecified edges take the default colour, and None values result in the edge being omitted. (Only supported in the SVG format.)

• time_scale (str) – Control how height values for nodes are computed. If this is equal to "time", node heights are proportional to their time values. If this is equal to "log_time", node heights are proportional to their log(time) values. If it is equal to "rank", node heights are spaced equally according to their ranked times. For SVG output the default is ‘time’-scale whereas for text output the default is ‘rank’-scale. Time scaling is not currently supported for text output.

• tree_height_scale (str) – Deprecated alias for time_scale. (Deprecated in 0.3.6)

• max_time (str,float) – The maximum time value in the current scaling system (see time_scale). Can be either a string or a numeric value. If equal to "tree", the maximum time is set to be that of the oldest root in the tree. If equal to "ts" the maximum time is set to be the time of the oldest root in the tree sequence; this is useful when drawing trees from the same tree sequence as it ensures that node heights are consistent. If a numeric value, this is used as the maximum time by which to scale other nodes. This parameter is not currently supported for text output.

• max_tree_height (str) – Deprecated alias for max_time. (Deprecated in 0.3.6)

• order (str) – The left-to-right ordering of child nodes in the drawn tree. This can be either: "minlex", which minimises the differences between adjacent trees (see also the "minlex_postorder" traversal order for the nodes() method); or "tree" which draws trees in the left-to-right order defined by the quintuply linked tree structure. If not specified or None, this defaults to "minlex".

Returns

A representation of this tree in the requested format.

Return type

str

draw_svg(path=None, *, size=None, time_scale=None, tree_height_scale=None, max_time=None, max_tree_height=None, node_labels=None, mutation_labels=None, root_svg_attributes=None, style=None, order=None, force_root_branch=None, symbol_size=None, x_axis=None, x_label=None, y_axis=None, y_label=None, y_ticks=None, y_gridlines=None, all_edge_mutations=None, **kwargs)[source]

Return an SVG representation of a single tree. By default, numeric labels are drawn beside nodes and mutations: these can be altered using the node_labels and mutation_labels parameters. See the visualization tutorial for more details.

Parameters
• path (str) – The path to the file to write the output. If None, do not write to file.

• size (tuple(int, int)) – A tuple of (width, height) giving the width and height of the produced SVG drawing in abstract user units (usually interpreted as pixels on initial display).

• time_scale (str) – Control how height values for nodes are computed. If this is equal to "time" (the default), node heights are proportional to their time values. If this is equal to "log_time", node heights are proportional to their log(time) values. If it is equal to "rank", node heights are spaced equally according to their ranked times.

• tree_height_scale (str) – Deprecated alias for time_scale. (Deprecated in 0.3.6)

• max_time (str,float) – The maximum time value in the current scaling system (see time_scale). Can be either a string or a numeric value. If equal to "tree" (the default), the maximum time is set to be that of the oldest root in the tree. If equal to "ts" the maximum time is set to be the time of the oldest root in the tree sequence; this is useful when drawing trees from the same tree sequence as it ensures that node heights are consistent. If a numeric value, this is used as the maximum time by which to scale other nodes.

• max_tree_height (str,float) – Deprecated alias for max_time. (Deprecated in 0.3.6)

• node_labels (dict(int, str)) – If specified, show custom labels for the nodes (specified by ID) that are present in this map; any nodes not present will not have a label.

• mutation_labels (dict(int, str)) – If specified, show custom labels for the mutations (specified by ID) that are present in the map; any mutations not present will not have a label.

• root_svg_attributes (dict) – Additional attributes, such as an id, that will be embedded in the root <svg> tag of the generated drawing.

• style (str) – A css style string that will be included in the <style> tag of the generated svg.

• order (str) – The left-to-right ordering of child nodes in the drawn tree. This can be either: "minlex", which minimises the differences between adjacent trees (see also the "minlex_postorder" traversal order for the nodes() method); or "tree" which draws trees in the left-to-right order defined by the quintuply linked tree structure. If not specified or None, this defaults to "minlex".

• force_root_branch (bool) – If True always plot a branch (edge) above the root(s) in the tree. If None (default) then only plot such root branches if there is a mutation above a root of the tree.

• symbol_size (float) – Change the default size of the node and mutation plotting symbols. If None (default) use a standard size.

• x_axis (bool) – Should the plot have an X axis line, showing the start and end position of this tree along the genome. If None (default) do not plot an X axis.

• x_label (str) – Place a label under the plot. If None (default) and there is an X axis, create and place an appropriate label.

• y_axis (bool) – Should the plot have an Y axis line, showing time (or ranked node time if time_scale="rank"). If None (default) do not plot a Y axis.

• y_label (str) – Place a label to the left of the plot. If None (default) and there is a Y axis, create and place an appropriate label.

• y_ticks (list) – A list of Y values at which to plot tickmarks ([] gives no tickmarks). If None, plot one tickmark for each unique node value.

• y_gridlines (bool) – Whether to plot horizontal lines behind the tree at each y tickmark.

• all_edge_mutations (bool) – The edge on which a mutation occurs may span multiple trees. If False or None (default) mutations are only drawn on an edge if their site position exists within the genomic interval covered by this tree. If True, all mutations on each edge of the tree are drawn, even if the their genomic position is to the left or right of the tree itself. Note that this means that independent drawings of different trees from the same tree sequence may share some plotted mutations.

Returns

An SVG representation of a tree.

Return type

str

draw_text(orientation=None, *, node_labels=None, max_time=None, use_ascii=False, order=None)[source]

Create a text representation of a tree.

Parameters
• orientation (str) – one of "top", "left", "bottom", or "right", specifying the margin on which the root is placed. Specifying "left" or "right" will lead to time being shown on the x axis (i.e. a “horizontal” tree. If None (default) use the standard coalescent arrangement of a vertical tree with recent nodes at the bottom of the plot and older nodes above.

• node_labels (dict) – If specified, show custom labels for the nodes that are present in the map. Any nodes not specified in the map will not have a node label.

• max_time (str) – If equal to "tree" (the default), the maximum time is set to be that of the oldest root in the tree. If equal to "ts" the maximum time is set to be the time of the oldest root in the tree sequence; this is useful when drawing trees from the same tree sequence as it ensures that node heights are consistent.

• use_ascii (bool) –

If False (default) then use unicode box drawing characters to render the tree. If True, use plain ascii characters, which look cruder but are less susceptible to misalignment or font substitution. Alternatively, if you are having alignment problems with Unicode, you can try out the solution documented here.

• order (str) – The left-to-right ordering of child nodes in the drawn tree. This can be either: "minlex", which minimises the differences between adjacent trees (see also the "minlex_postorder" traversal order for the nodes() method); or "tree" which draws trees in the left-to-right order defined by the quintuply linked tree structure. If not specified or None, this defaults to "minlex".

Returns

A text representation of a tree.

Return type

str

first()[source]

Seeks to the first tree in the sequence. This can be called whether the tree is in the null state or not.

static generate_balanced(num_leaves, *, arity=2, span=1, branch_length=1, record_provenance=True, **kwargs)[source]

Generate a Tree with the specified number of leaves that is maximally balanced. By default, the tree returned is binary, such that for each node that subtends $$n$$ leaves, the left child will subtend $$\lfloor{n / 2}\rfloor$$ leaves and the right child the remainder. Balanced trees with higher arity can also generated using the arity parameter, where the leaves subtending a node are distributed among its children analogously.

In the returned tree, the leaf nodes are all at time 0, marked as samples, and labelled 0 to n from left-to-right. Internal node IDs are assigned sequentially from n in a postorder traversal, and the time of an internal node is the maximum time of its children plus the specified branch_length.

Parameters
• num_leaves (int) – The number of leaf nodes in the returned tree (must be be 2 or greater).

• arity (int) – The maximum number of children a node can have in the returned tree.

• span (float) – The span of the tree, and therefore the sequence_length of the tree_sequence property of the returned Tree.

• branch_length (float) – The minimum length of a branch in the tree (see above for details on how internal node times are assigned).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example tskit.Tree.generate_balanced(sample_lists=True) will return a Tree created with sample_lists=True.

Returns

A balanced tree. Its corresponding TreeSequence is available via the tree_sequence attribute.

Return type

Tree

static generate_comb(num_leaves, *, span=1, branch_length=1, record_provenance=True, **kwargs)[source]

Generate a Tree in which all internal nodes have two children and the left child is a leaf. This is a “comb”, “ladder” or “pectinate” phylogeny, and also known as a caterpillar tree.

The leaf nodes are all at time 0, marked as samples, and labelled 0 to n from left-to-right. Internal node IDs are assigned sequentially from n as we ascend the tree, and the time of an internal node is the maximum time of its children plus the specified branch_length.

Parameters
• num_leaves (int) – The number of leaf nodes in the returned tree (must be 2 or greater).

• span (float) – The span of the tree, and therefore the sequence_length of the tree_sequence property of the returned Tree.

• branch_length (float) – The branch length between each internal node; the root node is therefore placed at time branch_length * (num_leaves - 1).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example tskit.Tree.generate_comb(sample_lists=True) will return a Tree created with sample_lists=True.

Returns

A comb-shaped bifurcating tree. Its corresponding TreeSequence is available via the tree_sequence attribute.

Return type

Tree

static generate_random_binary(num_leaves, *, span=1, branch_length=1, random_seed=None, record_provenance=True, **kwargs)[source]

Generate a random binary Tree with $$n$$ = num_leaves leaves with an equal probability of returning any topology and leaf label permutation among the $$(2n - 3)! / (2^{n - 2} (n - 2)!)$$ leaf-labelled binary trees.

The leaf nodes are marked as samples, labelled 0 to n, and placed at time 0. Internal node IDs are assigned sequentially from n as we ascend the tree, and the time of an internal node is the maximum time of its children plus the specified branch_length.

Note

The returned tree has not been created under any explicit model of evolution. In order to simulate such trees, additional software such as msprime <https://github.com/tskit-dev/msprime> is required.

Parameters
• num_leaves (int) – The number of leaf nodes in the returned tree (must be 2 or greater).

• span (float) – The span of the tree, and therefore the sequence_length of the tree_sequence property of the returned Tree.

• branch_length (float) – The minimum time between parent and child nodes.

• random_seed (int) – The random seed. If this is None, a random seed will be automatically generated. Valid random seeds must be between 1 and $$2^32 − 1$$.

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example tskit.Tree.generate_comb(sample_lists=True) will return a Tree created with sample_lists=True.

Returns

A random binary tree. Its corresponding TreeSequence is available via the tree_sequence attribute.

Return type

Tree

static generate_star(num_leaves, *, span=1, branch_length=1, record_provenance=True, **kwargs)[source]

Generate a Tree whose leaf nodes all have the same parent (i.e., a “star” tree). The leaf nodes are all at time 0 and are marked as sample nodes.

The tree produced by this method is identical to tskit.Tree.unrank(n, (0, 0)), but generated more efficiently for large n.

Parameters
• num_leaves (int) – The number of leaf nodes in the returned tree (must be 2 or greater).

• span (float) – The span of the tree, and therefore the sequence_length of the tree_sequence property of the returned Tree.

• branch_length (float) – The length of every branch in the tree (equivalent to the time of the root node).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example tskit.Tree.generate_star(sample_lists=True) will return a Tree created with sample_lists=True.

Returns

A star-shaped tree. Its corresponding TreeSequence is available via the tree_sequence attribute.

Return type

Tree

property has_multiple_roots

True if this tree has more than one root, False otherwise. Equivalent to tree.num_roots > 1. This is a O(1) operation.

Return type

bool

property has_single_root

True if this tree has a single root, False otherwise. Equivalent to tree.num_roots == 1. This is a O(1) operation.

Return type

bool

property index

Returns the index this tree occupies in the parent tree sequence. This index is zero based, so the first tree in the sequence has index 0.

Returns

The index of this tree.

Return type

int

property interval

Returns the coordinates of the genomic interval that this tree represents the history of. The interval is returned as a tuple $$(l, r)$$ and is a half-open interval such that the left coordinate is inclusive and the right coordinate is exclusive. This tree therefore applies to all genomic locations $$x$$ such that $$l \leq x < r$$.

Returns

A named tuple (l, r) representing the left-most (inclusive) and right-most (exclusive) coordinates of the genomic region covered by this tree. The coordinates can be accessed by index (0 or 1) or equivalently by name (.left or .right)

Return type

tuple

is_descendant(u, v)[source]

Returns True if the specified node u is a descendant of node v and False otherwise. A node $$u$$ is a descendant of another node $$v$$ if $$v$$ is on the path from $$u$$ to root. A node is considered to be a descendant of itself, so tree.is_descendant(u, u) will be True for any valid node.

Parameters
• u (int) – The descendant node.

• v (int) – The ancestral node.

Returns

True if u is a descendant of v.

Return type

bool

Raises

ValueError – If u or v are not valid node IDs.

is_internal(u)[source]

Returns True if the specified node is not a leaf. A node is internal if it has one or more children in the current tree.

Parameters

u (int) – The node of interest.

Returns

True if u is not a leaf node.

Return type

bool

is_isolated(u)[source]

Returns True if the specified node is isolated in this tree: that is it has no parents and no children. Sample nodes that are isolated and have no mutations above them are used to represent missing data.

Parameters

u (int) – The node of interest.

Returns

True if u is an isolated node.

Return type

bool

is_leaf(u)[source]

Returns True if the specified node is a leaf. A node $$u$$ is a leaf if it has zero children.

Parameters

u (int) – The node of interest.

Returns

True if u is a leaf node.

Return type

bool

is_sample(u)[source]

Returns True if the specified node is a sample. A node $$u$$ is a sample if it has been marked as a sample in the parent tree sequence.

Parameters

u (int) – The node of interest.

Returns

True if u is a sample.

Return type

bool

kc_distance(other, lambda_=0.0)[source]

Returns the Kendall-Colijn distance between the specified pair of trees. The lambda_ parameter determines the relative weight of topology vs branch lengths in calculating the distance. If lambda_ is 0 (the default) we only consider topology, and if it is 1 we only consider branch lengths. See Kendall & Colijn (2016) for details.

The trees we are comparing to must have identical lists of sample nodes (i.e., the same IDs in the same order). The metric operates on samples, not leaves, so internal samples are treated identically to sample tips. Subtrees with no samples do not contribute to the metric.

Parameters
• other (Tree) – The other tree to compare to.

• lambda (float) – The KC metric lambda parameter determining the relative weight of topology and branch length.

Returns

The computed KC distance between this tree and other.

Return type

float

last()[source]

Seeks to the last tree in the sequence. This can be called whether the tree is in the null state or not.

leaves(u=None)[source]

Returns an iterator over all the leaves in this tree that are underneath the specified node. If u is not specified, return all leaves in the tree.

Parameters

u (int) – The node of interest.

Returns

An iterator over all leaves in the subtree rooted at u.

Return type

collections.abc.Iterable

left_child(u)[source]

Returns the leftmost child of the specified node. Returns tskit.NULL if u is a leaf or is not a node in the current tree. The left-to-right ordering of children is arbitrary and should not be depended on; see the data model section for details.

This is a low-level method giving access to the quintuply linked tree structure in memory; the children() method is a more convenient way to obtain the children of a given node.

Parameters

u (int) – The node of interest.

Returns

The leftmost child of u.

Return type

int

property left_child_array

A numpy array (dtype=np.int32) encoding the left child of each node in this tree, such that tree.left_child_array[u] == tree.left_child(u) for all 0 <= u < ts.num_nodes. See the left_child() method for details on the semantics of tree left_child and the Tree structure section for information on the quintuply linked tree encoding.

Warning

This is a high-performance interface which provides zero-copy access to memory used in the C library. As a consequence, the values stored in this array will change as the Tree state is modified as we move along the tree sequence. See the Tree documentation for more details. Therefore, if you want to compare arrays representing different trees along the sequence, you must take copies of the arrays.

property left_root

The leftmost root in this tree. If there are multiple roots in this tree, they are siblings of this node, and so we can use right_sib() to iterate over all roots:

u = tree.left_root
while u != tskit.NULL:
print("Root:", u)
u = tree.right_sib(u)


The left-to-right ordering of roots is arbitrary and should not be depended on; see the data model section for details.

This is a low-level method giving access to the quintuply linked tree structure in memory; the roots attribute is a more convenient way to obtain the roots of a tree. If you are assuming that there is a single root in the tree you should use the root property.

Warning

Do not use this property if you are assuming that there is a single root in trees that are being processed. The root property should be used in this case, as it will raise an error when multiple roots exists.

Return type

int

left_sib(u)[source]

Returns the sibling node to the left of u, or tskit.NULL if u does not have a left sibling. The left-to-right ordering of children is arbitrary and should not be depended on; see the data model section for details.

Parameters

u (int) – The node of interest.

Returns

The sibling node to the left of u.

Return type

int

property left_sib_array

A numpy array (dtype=np.int32) encoding the left sib of each node in this tree, such that tree.left_sib_array[u] == tree.left_sib(u) for all 0 <= u < ts.num_nodes. See the left_sib() method for details on the semantics of tree left_sib and the Tree structure section for information on the quintuply linked tree encoding.

Warning

This is a high-performance interface which provides zero-copy access to memory used in the C library. As a consequence, the values stored in this array will change as the Tree state is modified as we move along the tree sequence. See the Tree documentation for more details. Therefore, if you want to compare arrays representing different trees along the sequence, you must take copies of the arrays.

map_mutations(genotypes, alleles, ancestral_state=None)[source]

Given observations for the samples in this tree described by the specified set of genotypes and alleles, return a parsimonious set of state transitions explaining these observations. The genotypes array is interpreted as indexes into the alleles list in the same manner as described in the TreeSequence.variants() method. Thus, if sample j carries the allele at index k, then we have genotypes[j] = k. Missing observations can be specified for a sample using the value tskit.MISSING_DATA (-1), in which case the state at this sample does not influence the ancestral state or the position of mutations returned. At least one non-missing observation must be provided. A maximum of 64 alleles are supported.

The current implementation uses the Hartigan parsimony algorithm to determine the minimum number of state transitions required to explain the data. In this model, transitions between any of the non-missing states is equally likely.

The returned values correspond directly to the data model for describing variation at sites using mutations. See the Site Table and Mutation Table definitions for details and background.

The state reconstruction is returned as two-tuple, (ancestral_state, mutations), where ancestral_state is the allele assigned to the tree root(s) and mutations is a list of Mutation objects, ordered as required in a mutation table. For each mutation, derived_state is the new state after this mutation and node is the tree node immediately beneath the mutation (if there are unary nodes between two branch points, hence multiple nodes above which the mutation could be parsimoniously placed, the oldest node is used). The parent property contains the index in the returned list of the previous mutation on the path to root, or tskit.NULL if there are no previous mutations (see the Mutation Table for more information on the concept of mutation parents). All other attributes of the Mutation object are undefined and should not be used.

Note

Sample states observed as missing in the input genotypes need not correspond to samples whose nodes are actually “missing” (i.e., isolated) in the tree. In this case, mapping the mutations returned by this method onto the tree will result in these missing observations being imputed to the most parsimonious state.

See the Parsimony section in the tutorial for examples of how to use this method.

Parameters
• genotypes (array_like) – The input observations for the samples in this tree.

• alleles (tuple(str)) – The alleles for the specified genotypes. Each positive value in the genotypes array is treated as an index into this list of alleles.

• ancestral_state (Union[int, str]) – A fixed ancestral state, specified either as a non-negative integer less than the number of alleles, or a string which must be one of the alleles provided above. If None (default) then an ancestral state is chosen arbitrarily from among those that provide the most parsimonious placement of mutations. Note that if the ancestral state is specified, the placement of mutations may not be as parsimonious as that which could be achieved by leaving the ancestral state unspecified; additionally it may lead to mutations being placed above the root node(s) of the tree (for example if all the samples have a genotype of 1 but the ancestral state is fixed to be 0).

Returns

The inferred ancestral state and list of mutations on this tree that encode the specified observations.

Return type
mrca(u, v)[source]

Returns the most recent common ancestor of the specified nodes.

Parameters
• u (int) – The first node.

• v (int) – The second node.

Returns

The most recent common ancestor of u and v.

Return type

int

mutations()[source]

Returns an iterator over all the mutations in this tree. Mutations are returned in their order in the mutations table, that is, by nondecreasing site ID, and within a site, by decreasing mutation time with parent mutations before their children. See the Mutation class for details on the available fields for each mutation.

The returned iterator is equivalent to iterating over all sites and all mutations in each site, i.e.:

>>> for site in tree.sites():
>>>     for mutation in site.mutations:
>>>         yield mutation

Returns

An iterator over all Mutation objects in this tree.

Return type

iter(Mutation)

newick(precision=14, *, root=None, node_labels=None, include_branch_lengths=True)[source]

Returns a newick encoding of this tree. If the root argument is specified, return a representation of the specified subtree, otherwise the full tree is returned. If the tree has multiple roots then separate newick strings for each rooted subtree must be found (i.e., we do not attempt to concatenate the different trees).

By default, leaf nodes are labelled with their numerical ID + 1, and internal nodes are not labelled. Arbitrary node labels can be specified using the node_labels argument, which maps node IDs to the desired labels.

Warning

Node labels are not Newick escaped, so care must be taken to provide labels that will not break the encoding.

Parameters
• precision (int) – The numerical precision with which branch lengths are printed.

• root (int) – If specified, return the tree rooted at this node.

• node_labels (dict) – If specified, show custom labels for the nodes that are present in the map. Any nodes not specified in the map will not have a node label.

• include_branch_lengths – If True (default), output branch lengths in the Newick string. If False, only output the topology, without branch lengths.

Returns

A newick representation of this tree.

Return type

str

next()[source]

Seeks to the next tree in the sequence. If the tree is in the initial null state we seek to the first tree (equivalent to calling first()). Calling next on the last tree in the sequence results in the tree being cleared back into the null initial state (equivalent to calling clear()). The return value of the function indicates whether the tree is in a non-null state, and can be used to loop over the trees:

# Iterate over the trees from left-to-right
tree = tskit.Tree(tree_sequence)
while tree.next()
# Do something with the tree.
print(tree.index)
# tree is now back in the null state.

Returns

True if the tree has been transformed into one of the trees in the sequence; False if the tree has been transformed into the null state.

Return type

bool

nodes(root=None, order='preorder')[source]

Returns an iterator over the node IDs reachable from the root(s) in this tree. See Tree.roots() for which nodes are considered roots. If the root parameter is provided, only the subtree rooted at this single root node will be iterated over. If this parameter is None, iterate over the node IDs in the subtrees rooted at each root node in turn. If the order parameter is provided, iterate over the nodes in each subtree in the specified tree traversal order.

Note

Unlike the TreeSequence.nodes() method, this iterator produces integer node IDs, not Node objects.

The currently implemented traversal orders are:

• ‘preorder’: starting at root, yield the current node, then recurse and do a preorder on each child of the current node. See also Wikipedia.

• ‘inorder’: starting at root, assuming binary trees, recurse and do an inorder on the first child, then yield the current node, then recurse and do an inorder on the second child. In the case of n child nodes (not necessarily 2), the first n // 2 children are visited in the first stage, and the remaining n - n // 2 children are visited in the second stage. See also Wikipedia.

• ‘postorder’: starting at root, recurse and do a postorder on each child of the current node, then yield the current node. See also Wikipedia.

• ‘levelorder’ (‘breadthfirst’): visit the nodes under root (including the root) in increasing order of their depth from root. See also Wikipedia.

• ‘timeasc’: visits the nodes in order of increasing time, falling back to increasing ID if times are equal.

• ‘timedesc’: visits the nodes in order of decreasing time, falling back to decreasing ID if times are equal.

• ‘minlex_postorder’: a usual postorder has ambiguity in the order in which children of a node are visited. We constrain this by outputting a postorder such that the leaves visited, when their IDs are listed out, have minimum lexicographic order out of all valid traversals. This traversal is useful for drawing multiple trees of a TreeSequence, as it leads to more consistency between adjacent trees. Note that internal non-leaf nodes are not counted in assessing the lexicographic order.

Parameters
• root (int) – The root of the subtree we are traversing.

• order (str) – The traversal ordering. Currently ‘preorder’, ‘inorder’, ‘postorder’, ‘levelorder’ (‘breadthfirst’), ‘timeasc’ and ‘timedesc’ and ‘minlex_postorder’ are supported.

Returns

An iterator over the node IDs in the tree in some traversal order.

Return type
num_children(u)[source]

Returns the number of children of the specified node (i.e., len(tree.children(u)))

Parameters

u (int) – The node of interest.

Returns

The number of immediate children of the node u in this tree.

Return type

int

property num_mutations

Returns the total number of mutations across all sites on this tree.

Returns

The total number of mutations over all sites on this tree.

Return type

int

property num_nodes

Returns the number of nodes in the TreeSequence this tree is in. Equivalent to tree.tree_sequence.num_nodes. To find the number of nodes that are reachable from all roots use len(list(tree.nodes())).

Return type

int

property num_roots

The number of roots in this tree, as defined in the roots attribute.

Only requires O(number of roots) time.

Return type

int

num_samples(u=None)[source]

Returns the number of samples in this tree underneath the specified node (including the node itself). If u is not specified return the total number of samples in the tree.

This is a constant time operation.

Parameters

u (int) – The node of interest.

Returns

The number of samples in the subtree rooted at u.

Return type

int

property num_sites

Returns the number of sites on this tree.

Returns

The number of sites on this tree.

Return type

int

num_tracked_samples(u=None)[source]

Returns the number of samples in the set specified in the tracked_samples parameter of the TreeSequence.trees() method underneath the specified node. If the input node is not specified, return the total number of tracked samples in the tree.

This is a constant time operation.

Parameters

u (int) – The node of interest.

Returns

The number of samples within the set of tracked samples in the subtree rooted at u.

Return type

int

parent(u)[source]

Returns the parent of the specified node. Returns tskit.NULL if u is a root or is not a node in the current tree.

Parameters

u (int) – The node of interest.

Returns

The parent of u.

Return type

int

property parent_array

A numpy array (dtype=np.int32) encoding the parent of each node in this tree, such that tree.parent_array[u] == tree.parent(u) for all 0 <= u < ts.num_nodes. See the parent() method for details on the semantics of tree parents and the Tree structure section for information on the quintuply linked tree encoding.

Warning

This is a high-performance interface which provides zero-copy access to memory used in the C library. As a consequence, the values stored in this array will change as the Tree state is modified as we move along the tree sequence. See the Tree documentation for more details. Therefore, if you want to compare arrays representing different trees along the sequence, you must take copies of the arrays.

population(u)[source]

Returns the population associated with the specified node. Equivalent to tree.tree_sequence.node(u).population.

Parameters

u (int) – The node of interest.

Returns

The ID of the population associated with node u.

Return type

int

prev()[source]

Seeks to the previous tree in the sequence. If the tree is in the initial null state we seek to the last tree (equivalent to calling last()). Calling prev on the first tree in the sequence results in the tree being cleared back into the null initial state (equivalent to calling clear()). The return value of the function indicates whether the tree is in a non-null state, and can be used to loop over the trees:

# Iterate over the trees from right-to-left
tree = tskit.Tree(tree_sequence)
while tree.prev()
# Do something with the tree.
print(tree.index)
# tree is now back in the null state.

Returns

True if the tree has been transformed into one of the trees in the sequence; False if the tree has been transformed into the null state.

Return type

bool

rank()[source]

Produce the rank of this tree in the enumeration of all leaf-labelled trees of n leaves. See the Interpreting Tree Ranks section for details on ranking and unranking trees.

Return type

tuple(int)

Raises

ValueError – If the tree has multiple roots.

right_child(u)[source]

Returns the rightmost child of the specified node. Returns tskit.NULL if u is a leaf or is not a node in the current tree. The left-to-right ordering of children is arbitrary and should not be depended on; see the data model section for details.

This is a low-level method giving access to the quintuply linked tree structure in memory; the children() method is a more convenient way to obtain the children of a given node.

Parameters

u (int) – The node of interest.

Returns

The rightmost child of u.

Return type

int

property right_child_array

A numpy array (dtype=np.int32) encoding the right child of each node in this tree, such that tree.right_child_array[u] == tree.right_child(u) for all 0 <= u < ts.num_nodes. See the right_child() method for details on the semantics of tree right_child and the Tree structure section for information on the quintuply linked tree encoding.

Warning

This is a high-performance interface which provides zero-copy access to memory used in the C library. As a consequence, the values stored in this array will change as the Tree state is modified as we move along the tree sequence. See the Tree documentation for more details. Therefore, if you want to compare arrays representing different trees along the sequence, you must take copies of the arrays.

right_sib(u)[source]

Returns the sibling node to the right of u, or tskit.NULL if u does not have a right sibling. The left-to-right ordering of children is arbitrary and should not be depended on; see the data model section for details.

Parameters

u (int) – The node of interest.

Returns

The sibling node to the right of u.

Return type

int

property right_sib_array

A numpy array (dtype=np.int32) encoding the right sib of each node in this tree, such that tree.right_sib_array[u] == tree.right_sib(u) for all 0 <= u < ts.num_nodes. See the right_sib() method for details on the semantics of tree right_sib and the Tree structure section for information on the quintuply linked tree encoding.

Warning

This is a high-performance interface which provides zero-copy access to memory used in the C library. As a consequence, the values stored in this array will change as the Tree state is modified as we move along the tree sequence. See the Tree documentation for more details. Therefore, if you want to compare arrays representing different trees along the sequence, you must take copies of the arrays.

property root

The root of this tree. If the tree contains multiple roots, a ValueError is raised indicating that the roots attribute should be used instead.

Returns

The root node.

Return type

int

Raises

ValueError if this tree contains more than one root.

property root_threshold

Returns the minimum number of samples that a node must be an ancestor of to be considered a potential root.

Returns

The root threshold.

Return type

TreeSequence

property roots

The list of roots in this tree. A root is defined as a unique endpoint of the paths starting at samples. We can define the set of roots as follows:

roots = set()
for u in tree_sequence.samples():
while tree.parent(u) != tskit.NULL:
u = tree.parent(u)
# roots is now the set of all roots in this tree.
assert sorted(roots) == sorted(tree.roots)


The roots of the tree are returned in a list, in no particular order.

Only requires O(number of roots) time.

Returns

The list of roots in this tree.

Return type

list

property sample_size

Returns the sample size for this tree. This is the number of sample nodes in the tree.

Returns

The number of sample nodes in the tree.

Return type

int

samples(u=None)[source]

Returns an iterator over the numerical IDs of all the sample nodes in this tree that are underneath node u. If u is a sample, it is included in the returned iterator. If u is not specified, return all sample node IDs in the tree.

If the TreeSequence.trees() method is called with sample_lists=True, this method uses an efficient algorithm to find the sample nodes. If not, a simple traversal based method is used.

Note

The iterator is not guaranteed to return the sample node IDs in numerical or any other particular order.

Parameters

u (int) – The node of interest.

Returns

An iterator over all sample node IDs in the subtree rooted at u.

Return type

collections.abc.Iterable

seek(position)[source]

Sets the state to represent the tree that covers the specified position in the parent tree sequence. After a successful return of this method we have tree.interval.left <= position < tree.interval.right.

Parameters

position (float) – The position along the sequence length to seek to.

Raises

ValueError – If 0 < position or position >= TreeSequence.sequence_length.

seek_index(index)[source]

Sets the state to represent the tree at the specified index in the parent tree sequence. Negative indexes following the standard Python conventions are allowed, i.e., index=-1 will seek to the last tree in the sequence.

Parameters

index (int) – The tree index to seek to.

Raises

IndexError – If an index outside the acceptable range is provided.

sites()[source]

Returns an iterator over all the sites in this tree. Sites are returned in order of increasing ID (and also position). See the Site class for details on the available fields for each site.

Returns

An iterator over all sites in this tree.

property span

Returns the genomic distance that this tree spans. This is defined as $$r - l$$, where $$(l, r)$$ is the genomic interval returned by interval.

Returns

The genomic distance covered by this tree.

Return type

float

split_polytomies(*, epsilon=None, method=None, record_provenance=True, random_seed=None, **kwargs)[source]

Return a new Tree where extra nodes and edges have been inserted so that any any node u with greater than 2 children — a multifurcation or “polytomy” — is resolved into successive bifurcations. New nodes are inserted at times fractionally less than than the time of node u. Times are allocated to different levels of the tree, such that any newly inserted sibling nodes will have the same time.

By default, the times of the newly generated children of a particular node are the minimum representable distance in floating point arithmetic from their parents (using the nextafter function). Thus, the generated branches have the shortest possible nonzero length. A fixed branch length between inserted nodes and their parents can also be specified by using the epsilon parameter.

Note

A tree sequence requires that parents be older than children and that mutations are younger than the parent of the edge on which they lie. If a fixed epsilon is specifed and is not small enough compared to the distance between a polytomy and its oldest child (or oldest child mutation) these requirements may not be met. In this case an error will be raised.

If the method is "random" (currently the only option, and the default when no method is specified), then for a node with $$n$$ children, the $$(2n - 3)! / (2^(n - 2) (n - 2!))$$ possible binary trees with equal probability.

The returned :class.Tree will have the same genomic span as this tree, and node IDs will be conserved (that is, node u in this tree will be the same node in the returned tree). The returned tree is derived from a tree sequence that contains only one non-degenerate tree, that is, where edges cover only the interval spanned by this tree.

Parameters
• epsilon – If specified, the fixed branch length between inserted nodes and their parents. If None (the default), the minimal possible nonzero branch length is generated for each node.

• method (str) – The method used to break polytomies. Currently only “random” is supported, which can also be specified by method=None (Default: None).

• record_provenance (bool) – If True, add details of this operation to the provenance information of the returned tree sequence. (Default: True).

• random_seed (int) – The random seed. If this is None, a random seed will be automatically generated. Valid random seeds must be between 1 and $$2^32 − 1$$.

• **kwargs – Further arguments used as parameters when constructing the returned Tree. For example tree.split_polytomies(sample_lists=True) will return a Tree created with sample_lists=True.

Returns

A new tree with polytomies split into random bifurcations.

Return type

tskit.Tree

time(u)[source]

Returns the time of the specified node. Equivalent to tree.tree_sequence.node(u).time.

Parameters

u (int) – The node of interest.

Returns

The time of u.

Return type

float

tmrca(u, v)[source]

Returns the time of the most recent common ancestor of the specified nodes. This is equivalent to:

>>> tree.time(tree.mrca(u, v))

Parameters
• u (int) – The first node.

• v (int) – The second node.

Returns

The time of the most recent common ancestor of u and v.

Return type

float

property total_branch_length

Returns the sum of all the branch lengths in this tree (in units of time). This is equivalent to

>>> sum(tree.branch_length(u) for u in tree.nodes())


Note that the branch lengths for root nodes are defined as zero.

As this is defined by a traversal of the tree, technically we return the sum of all branch lengths that are reachable from roots. Thus, this is the sum of all branches that are ancestral to at least one sample. This distinction is only important in tree sequences that contain ‘dead branches’, i.e., those that define topology not ancestral to any samples.

Returns

The sum of lengths of branches in this tree.

Return type

float

property tree_sequence

Returns the tree sequence that this tree is from.

Returns

The parent tree sequence for this tree.

Return type

TreeSequence

static unrank(num_leaves, rank, *, span=1, branch_length=1)[source]

Reconstruct the tree of the given rank (see tskit.Tree.rank()) with num_leaves leaves. The labels and times of internal nodes are assigned by a postorder traversal of the nodes, such that the time of each internal node is the maximum time of its children plus the specified branch_length. The time of each leaf is 0.

See the Interpreting Tree Ranks section for details on ranking and unranking trees and what constitutes valid ranks.

Parameters
• num_leaves (int) – The number of leaves of the tree to generate.

• rank (tuple(int)) – The rank of the tree to generate.

• span (float) – The genomic span of the returned tree. The tree will cover the interval $$[0, \text{span})$$ and the tree_sequence from which the tree is taken will have its sequence_length equal to span.

Param

float branch_length: The minimum length of a branch in this tree.

Return type

Tree

Raises

ValueError: If the given rank is out of bounds for trees with num_leaves leaves.

### Simple container classes¶

These classes are simple shallow containers representing the entities defined in the Definitions. These classes are not intended to be instantiated directly, but are the return types for the various iterators provided by the TreeSequence and Tree classes.

class tskit.Individual[source]

An individual in a tree sequence. Since nodes correspond to genomes, individuals are associated with a collection of nodes (e.g., two nodes per diploid). See Nodes, Genomes, or Individuals? for more discussion of this distinction.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

flags: int

The bitwise flags for this individual.

id: int

The integer ID of this individual. Varies from 0 to TreeSequence.num_individuals - 1.

location: numpy.ndarray

The spatial location of this individual as a numpy array. The location is an empty array if no spatial location is defined.

metadata: Optional[Union[bytes, dict]]

The metadata for this individual, decoded if a schema applies.

nodes: numpy.ndarray

The IDs of the nodes that are associated with this individual as a numpy array (dtype=np.int32). If no nodes are associated with the individual this array will be empty.

parents: numpy.ndarray

The parent individual ids of this individual as a numpy array. The parents is an empty array if no parents are defined.

class tskit.Node[source]

A node in a tree sequence, corresponding to a single genome. The time and population are attributes of the Node, rather than the Individual, as discussed in Nodes, Genomes, or Individuals?.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

flags: int

The bitwise flags for this node.

id: int

The integer ID of this node. Varies from 0 to TreeSequence.num_nodes - 1.

individual: int

The integer ID of the individual that this node was a part of.

is_sample()[source]

Returns True if this node is a sample. This value is derived from the flag variable.

Return type

bool

metadata: Optional[Union[bytes, dict]]

The metadata for this node, decoded if a schema applies.

population: int

The integer ID of the population that this node was born in.

time: float

The birth time of this node.

class tskit.Edge[source]

An edge in a tree sequence.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

child: int

The integer ID of the child node for this edge. To obtain further information about a node with a given ID, use TreeSequence.node().

id: int

The integer ID of this edge. Varies from 0 to TreeSequence.num_edges - 1.

left: float

The left coordinate of this edge.

metadata: Optional[Union[bytes, dict]]

The metadata for this edge, decoded if a schema applies.

parent: int

The integer ID of the parent node for this edge. To obtain further information about a node with a given ID, use TreeSequence.node().

right: float

The right coordinate of this edge.

property span

Returns the span of this edge, i.e., the right position minus the left position

Returns

The span of this edge.

Return type

float

class tskit.Interval[source]

A tuple of 2 numbers, [left, right), defining an interval over the genome.

Variables
• left (float) – The left hand end of the interval. By convention this value is included in the interval.

• right (float) – The right hand end of the interval. By convention this value is not included in the interval, i.e., the interval is half-open.

• span (float) – The span of the genome covered by this interval, simply right-left.

left: float

Alias for field number 0

right: float

Alias for field number 1

class tskit.Site[source]

A site in a tree sequence.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

ancestral_state: str

The ancestral state at this site (i.e., the state inherited by nodes, unless mutations occur).

id: int

The integer ID of this site. Varies from 0 to TreeSequence.num_sites - 1.

metadata: Optional[Union[bytes, dict]]

The metadata for this site, decoded if a schema applies.

mutations: numpy.ndarray

The list of mutations at this site. Mutations within a site are returned in the order they are specified in the underlying MutationTable.

position: float

The floating point location of this site in genome coordinates. Ranges from 0 (inclusive) to TreeSequence.sequence_length (exclusive).

class tskit.Mutation[source]

A mutation in a tree sequence.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

derived_state: str

The derived state for this mutation. This is the state inherited by nodes in the subtree rooted at this mutation’s node, unless another mutation occurs.

id: int

The integer ID of this mutation. Varies from 0 to TreeSequence.num_mutations - 1.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

metadata: Optional[Union[bytes, dict]]

The metadata for this mutation, decoded if a schema applies.

node: int

The integer ID of the first node that inherits this mutation. To obtain further information about a node with a given ID, use TreeSequence.node().

parent: int

The integer ID of this mutation’s parent mutation. When multiple mutations occur at a site along a path in the tree, mutations must record the mutation that is immediately above them. If the mutation does not have a parent, this is equal to the NULL (-1). To obtain further information about a mutation with a given ID, use TreeSequence.mutation().

site: int

The integer ID of the site that this mutation occurs at. To obtain further information about a site with a given ID use TreeSequence.site().

time: float

The occurrence time of this mutation.

class tskit.Variant[source]

A variant represents the observed variation among samples for a given site. A variant consists (a) of a reference to the Site instance in question; (b) the alleles that may be observed at the samples for this site; and (c) the genotypes mapping sample IDs to the observed alleles.

Each element in the alleles tuple is a string, representing the actual observed state for a given sample. The alleles tuple is generated in one of two ways. The first (and default) way is for tskit to generate the encoding on the fly as alleles are encountered while generating genotypes. In this case, the first element of this tuple is guaranteed to be the same as the site’s ancestral_state value and the list of alleles is also guaranteed not to contain any duplicates. Note that allelic values may be listed that are not referred to by any samples. For example, if we have a site that is fixed for the derived state (i.e., we have a mutation over the tree root), all genotypes will be 1, but the alleles list will be equal to ('0', '1'). Other than the ancestral state being the first allele, the alleles are listed in no particular order, and the ordering should not be relied upon (but see the notes on missing data below).

The second way is for the user to define the mapping between genotype values and allelic state strings using the alleles parameter to the TreeSequence.variants() method. In this case, there is no indication of which allele is the ancestral state, as the ordering is determined by the user.

The genotypes represent the observed allelic states for each sample, such that var.alleles[var.genotypes[j]] gives the string allele for sample ID j. Thus, the elements of the genotypes array are indexes into the alleles list. The genotypes are provided in this way via a numpy array to enable efficient calculations.

When missing data is present at a given site, the property has_missing_data will be True, at least one element of the genotypes array will be equal to tskit.MISSING_DATA, and the last element of the alleles array will be None. Note that in this case variant.num_alleles will not be equal to len(variant.alleles). The rationale for adding None to the end of the alleles list is to help code that does not handle missing data correctly fail early rather than introducing subtle and hard-to-find bugs. As tskit.MISSING_DATA is equal to -1, code that decodes genotypes into allelic values without taking missing data into account would otherwise incorrectly output the last allele in the list.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

alleles: tuple

A tuple of the allelic values that may be observed at the samples at the current site. The first element of this tuple is always the site’s ancestral state.

genotypes: numpy.ndarray

An array of indexes into the list alleles, giving the state of each sample at the current site.

property has_missing_data

True if there is missing data for any of the samples at the current site.

property num_alleles

The number of distinct alleles at this site. Note that this may be greater than the number of distinct values in the genotypes array.

site: tskit.trees.Site

The site object for this variant.

class tskit.Migration[source]

A migration in a tree sequence.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

dest: int

The destination population ID.

id: int

The integer ID of this mutation. Varies from 0 to TreeSequence.num_mutations - 1.

left: float

The left end of the genomic interval covered by this migration (inclusive).

metadata: Optional[Union[bytes, dict]]

The metadata for this migration, decoded if a schema applies.

node: int

The integer ID of the node involved in this migration event. To obtain further information about a node with a given ID, use TreeSequence.node().

right: float

The right end of the genomic interval covered by this migration (exclusive).

source: int

The source population ID.

time: float

The time at which this migration occurred at.

class tskit.Population[source]

A population in a tree sequence.

Modifying the attributes in this class will have no effect on the underlying tree sequence data.

id: int

The integer ID of this population. Varies from 0 to TreeSequence.num_populations - 1.

metadata: Optional[Union[bytes, dict]]

The metadata for this population, decoded if a schema applies.

class tskit.Provenance[source]

Provenance(id: int, timestamp: str, record: str)

There are several methods for loading data into a TreeSequence instance. The simplest and most convenient is the use the tskit.load() function to load a tree sequence file. For small scale data and debugging, it is often convenient to use the tskit.load_text() to read data in the text file format. The TableCollection.tree_sequence() function efficiently creates a TreeSequence object from a set of tables using the Tables API.

tskit.load(file)[source]

Loads a tree sequence from the specified file object or path. The file must be in the tree sequence file format produced by the TreeSequence.dump() method.

Parameters

file (str) – The file object or path of the .trees file containing the tree sequence we wish to load.

Returns

The tree sequence object containing the information stored in the specified file path.

Return type

tskit.TreeSequence

tskit.load_text(nodes, edges, sites=None, mutations=None, individuals=None, populations=None, sequence_length=0, strict=True, encoding='utf8', base64_metadata=True)[source]

Parses the tree sequence data from the specified file-like objects, and returns the resulting TreeSequence object. The format for these files is documented in the Text file formats section, and is produced by the TreeSequence.dump_text() method. Further properties required for an input tree sequence are described in the Valid tree sequence requirements section. This method is intended as a convenient interface for importing external data into tskit; the binary file format using by tskit.load() is many times more efficient than this text format.

The nodes and edges parameters are mandatory and must be file-like objects containing text with whitespace delimited columns, parsable by parse_nodes() and parse_edges(), respectively. sites, mutations, individuals and populations are optional, and must be parsable by parse_sites(), parse_individuals(), parse_populations(), and parse_mutations(), respectively.

The sequence_length parameter determines the TreeSequence.sequence_length of the returned tree sequence. If it is 0 or not specified, the value is taken to be the maximum right coordinate of the input edges. This parameter is useful in degenerate situations (such as when there are zero edges), but can usually be ignored.

The strict parameter controls the field delimiting algorithm that is used. If strict is True (the default), we require exactly one tab character separating each field. If strict is False, a more relaxed whitespace delimiting algorithm is used, such that any run of whitespace is regarded as a field separator. In most situations, strict=False is more convenient, but it can lead to error in certain situations. For example, if a deletion is encoded in the mutation table this will not be parseable when strict=False.

After parsing the tables, TableCollection.sort() is called to ensure that the loaded tables satisfy the tree sequence ordering requirements. Note that this may result in the IDs of various entities changing from their positions in the input file.

Parameters
Returns

The tree sequence object containing the information stored in the specified file paths.

Return type

tskit.TreeSequence

## Tables and Table Collections¶

The information required to construct a tree sequence is stored in a collection of tables, each defining a different aspect of the structure of a tree sequence. These tables are described individually in the next section. However, these are interrelated, and so many operations work on the entire collection of tables, known as a TableCollection. The TableCollection and TreeSequence classes are deeply related. A TreeSequence instance is based on the information encoded in a TableCollection. Tree sequences are immutable, and provide methods for obtaining trees from the sequence. A TableCollection is mutable, and does not have any methods for obtaining trees. The TableCollection class thus allows dynamic creation and modification of tree sequences.

### The TableCollection class¶

Many of the TreeSequence methods that return a modified tree sequence are in fact wrappers around a corresponding TableCollection method that modifies a copy of the origin tree sequence’s table collection.

class tskit.TableCollection(sequence_length=0)[source]

A collection of mutable tables defining a tree sequence. See the Data model section for definition on the various tables and how they together define a TreeSequence. Arbitrary data can be stored in a TableCollection, but there are certain requirements that must be satisfied for these tables to be interpreted as a tree sequence.

To obtain an immutable TreeSequence instance corresponding to the current state of a TableCollection, please use the tree_sequence() method.

Variables
• individuals (IndividualTable) – The individual table.

• nodes (NodeTable) – The node table.

• edges (EdgeTable) – The edge table.

• migrations (MigrationTable) – The migration table.

• sites (SiteTable) – The site table.

• mutations (MutationTable) – The mutation table.

• populations (PopulationTable) – The population table.

• provenances (ProvenanceTable) – The provenance table.

• index – The edge insertion and removal index.

• sequence_length (float) – The sequence length defining the coordinate space.

• file_uuid (str) – The UUID for the file this TableCollection is derived from, or None if not derived from a file.

Methods

 Returns a dictionary representation of this TableCollection. assert_equals(other, *[, ignore_metadata, …]) Raise an AssertionError for the first found difference between this and another table collection. Builds an index on this TableCollection. canonicalise([remove_unreferenced]) This puts the tables in canonical form - to do this, the individual and population tables are sorted by the first node that refers to each (see TreeSequence.subset()) Then, the remaining tables are sorted as in sort(), with the modification that mutations are sorted by site, then time, then number of descendant mutations (ensuring that parent mutations occur before children), then node, then original order in the tables. clear([clear_provenance, …]) Remove all rows of the data tables, optionally remove provenance, metadata schemas and ts-level metadata. Modifies the tables in place, computing the parent column of the mutation table. Modifies the tables in place, computing valid values for the time column of the mutation table. Returns a deep copy of this TableCollection. Modifies the tables in place, removing entries in the site table with duplicate position (and keeping only the first entry for each site), and renumbering the site column of the mutation table appropriately. delete_intervals(intervals[, simplify, …]) Delete all information from this set of tables which lies within the specified list of genomic intervals. delete_sites(site_ids[, record_provenance]) Remove the specified sites entirely from the sites and mutations tables in this collection. Drops any indexes present on this table collection. dump(file_or_path) Writes the table collection to the specified path or file object. equals(other, *[, ignore_metadata, …]) Returns True if self and other are equal. Returns True if this TableCollection is indexed. keep_intervals(intervals[, simplify, …]) Delete all information from this set of tables which lies outside the specified list of genomic intervals. link_ancestors(samples, ancestors) Returns an EdgeTable instance describing a subset of the genealogical relationships between the nodes in samples and ancestors. ltrim([record_provenance]) Reset the coordinate system used in these tables, changing the left and right genomic positions in the edge table such that the leftmost edge now starts at position 0. rtrim([record_provenance]) Reset the sequence_length property so that the sequence ends at the end of the last edge. simplify([samples, reduce_to_site_topology, …]) Simplifies the tables in place to retain only the information necessary to reconstruct the tree sequence describing the given samples. sort([edge_start]) Sorts the tables in place. subset(nodes[, record_provenance, …]) Modifies the tables in place to contain only the entries referring to the provided list of node IDs, with nodes reordered according to the order they appear in the list. Returns a TreeSequence instance with the structure defined by the tables in this TableCollection. trim([record_provenance]) Trim away any empty regions on the right and left of the tree sequence encoded by these tables. union(other, node_mapping[, …]) Modifies the table collection in place by adding the non-shared portions of other to itself.

Attributes

 metadata The decoded metadata for this TableCollection. metadata_bytes The raw bytes of metadata for this TableCollection metadata_schema The tskit.MetadataSchema for this TableCollection. name_map Returns a dictionary mapping table names to the corresponding table instances. nbytes Returns the total number of bytes required to store the data in this table collection.
asdict()[source]

Returns a dictionary representation of this TableCollection.

Note: the semantics of this method changed at tskit 0.1.0. Previously a map of table names to the tables themselves was returned.

assert_equals(other, *, ignore_metadata=False, ignore_ts_metadata=False, ignore_provenance=False, ignore_timestamps=False)[source]

Raise an AssertionError for the first found difference between this and another table collection. Note that table indexes are not checked.

Parameters
• other (TableCollection) – Another table collection.

• ignore_metadata (bool) – If True all metadata and metadata schemas will be excluded from the comparison. This includes the top-level tree sequence and constituent table metadata (default=False).

• ignore_ts_metadata (bool) – If True the top-level tree sequence metadata and metadata schemas will be excluded from the comparison. If ignore_metadata is True, this parameter has no effect.

• ignore_provenance (bool) – If True the provenance tables are not included in the comparison.

• ignore_timestamps (bool) – If True the provenance timestamp column is ignored in the comparison. If ignore_provenance is True, this parameter has no effect.

build_index()[source]

Builds an index on this TableCollection. Any existing indexes are automatically dropped.

canonicalise(remove_unreferenced=None)[source]

This puts the tables in canonical form - to do this, the individual and population tables are sorted by the first node that refers to each (see TreeSequence.subset()) Then, the remaining tables are sorted as in sort(), with the modification that mutations are sorted by site, then time, then number of descendant mutations (ensuring that parent mutations occur before children), then node, then original order in the tables. This ensures that any two tables with the same information should be identical after canonical sorting.

By default, the method removes sites, individuals, and populations that are not referenced (by mutations and nodes, respectively). If you wish to keep these, pass remove_unreferenced=False, but note that unreferenced individuals and populations are put at the end of the tables in their original order.

sort() for sorting edges, mutations, and sites, and subset() for reordering nodes, individuals, and populations.

Parameters

remove_unreferenced (bool) – Whether to remove unreferenced sites, individuals, and populations (default=True).

clear(clear_provenance=False, clear_metadata_schemas=False, clear_ts_metadata_and_schema=False)[source]

Remove all rows of the data tables, optionally remove provenance, metadata schemas and ts-level metadata.

Parameters
• clear_provenance (bool) – If True, remove all rows of the provenance table. (Default: False).

• clear_metadata_schemas (bool) – If True, clear the table metadata schemas. (Default: False).

• clear_ts_metadata_and_schema (bool) – If True, clear the tree-sequence level metadata and schema (Default: False).

compute_mutation_parents()[source]

Modifies the tables in place, computing the parent column of the mutation table. For this to work, the node and edge tables must be valid, and the site and mutation tables must be sorted (see TableCollection.sort()). This will produce an error if mutations are not sorted (i.e., if a mutation appears before its mutation parent) unless the two mutations occur on the same branch, in which case there is no way to detect the error.

The parent of a given mutation is the ID of the next mutation encountered traversing the tree upwards from that mutation, or NULL if there is no such mutation.

Note

note: This method does not check that all mutations result in a change of state, as required; see Mutation requirements.

compute_mutation_times()[source]

Modifies the tables in place, computing valid values for the time column of the mutation table. For this to work, the node and edge tables must be valid, and the site and mutation tables must be sorted and indexed(see TableCollection.sort() and TableCollection.build_index()).

For a single mutation on an edge at a site, the time assigned to a mutation by this method is the mid-point between the times of the nodes above and below the mutation. In the case where there is more than one mutation on an edge for a site, the times are evenly spread along the edge. For mutations that are above a root node, the time of the root node is assigned.

The mutation table will be sorted if the new times mean that the original order is no longer valid.

copy()[source]

Returns a deep copy of this TableCollection.

Returns

A deep copy of this TableCollection.

Return type

TableCollection

deduplicate_sites()[source]

Modifies the tables in place, removing entries in the site table with duplicate position (and keeping only the first entry for each site), and renumbering the site column of the mutation table appropriately. This requires the site table to be sorted by position.

Warning

This method does not sort the tables afterwards, so mutations may no longer be sorted by time.

delete_intervals(intervals, simplify=True, record_provenance=True)[source]

Delete all information from this set of tables which lies within the specified list of genomic intervals. This is identical to TreeSequence.delete_intervals() but acts in place to alter the data in this TableCollection.

Parameters
• intervals (array_like) – A list (start, end) pairs describing the genomic intervals to delete. Intervals must be non-overlapping and in increasing order. The list of intervals must be interpretable as a 2D numpy array with shape (N, 2), where N is the number of intervals.

• simplify (bool) – If True, run simplify on the tables so that nodes no longer used are discarded. (Default: True).

• record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

delete_sites(site_ids, record_provenance=True)[source]

Remove the specified sites entirely from the sites and mutations tables in this collection. This is identical to TreeSequence.delete_sites() but acts in place to alter the data in this TableCollection.

Parameters
• site_ids (list[int]) – A list of site IDs specifying the sites to remove.

• record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

drop_index()[source]

Drops any indexes present on this table collection. If the tables are not currently indexed this method has no effect.

dump(file_or_path)[source]

Writes the table collection to the specified path or file object.

Parameters

file_or_path (str) – The file object or path to write the TreeSequence to.

equals(other, *, ignore_metadata=False, ignore_ts_metadata=False, ignore_provenance=False, ignore_timestamps=False)[source]

Returns True if self and other are equal. By default, two table collections are considered equal if their

• sequence_length properties are identical;

• constituent tables are byte-wise identical.

Some of the requirements in this definition can be relaxed using the parameters, which can be used to remove certain parts of the data model from the comparison.

Table indexes are not considered in the equality comparison.

Parameters
• other (TableCollection) – Another table collection.

• ignore_metadata (bool) – If True all metadata and metadata schemas will be excluded from the comparison. This includes the top-level tree sequence and constituent table metadata (default=False).

• ignore_ts_metadata (bool) – If True the top-level tree sequence metadata and metadata schemas will be excluded from the comparison. If ignore_metadata is True, this parameter has no effect.

• ignore_provenance (bool) – If True the provenance tables are not included in the comparison.

• ignore_timestamps (bool) – If True the provenance timestamp column is ignored in the comparison. If ignore_provenance is True, this parameter has no effect.

Returns

True if other is equal to this table collection; False otherwise.

Return type

bool

has_index()[source]

Returns True if this TableCollection is indexed.

keep_intervals(intervals, simplify=True, record_provenance=True)[source]

Delete all information from this set of tables which lies outside the specified list of genomic intervals. This is identical to TreeSequence.keep_intervals() but acts in place to alter the data in this TableCollection.

Parameters
• intervals (array_like) – A list (start, end) pairs describing the genomic intervals to keep. Intervals must be non-overlapping and in increasing order. The list of intervals must be interpretable as a 2D numpy array with shape (N, 2), where N is the number of intervals.

• simplify (bool) – If True, run simplify on the tables so that nodes no longer used are discarded. Must be False if input tree sequence includes migrations. (Default: True).

• record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

Returns an EdgeTable instance describing a subset of the genealogical relationships between the nodes in samples and ancestors.

Each row parent, child, left, right in the output table indicates that child has inherited the segment [left, right) from parent more recently than from any other node in these lists.

In particular, suppose samples is a list of nodes such that time is 0 for each node, and ancestors is a list of nodes such that time is greater than 0.0 for each node. Then each row of the output table will show an interval [left, right) over which a node in samples has inherited most recently from a node in ancestors, or an interval over which one of these ancestors has inherited most recently from another node in ancestors.

The following table shows which parent->child pairs will be shown in the output of link_ancestors. A node is a relevant descendant on a given interval if it also appears somewhere in the parent column of the outputted table.

 Type of relationship Shown in output of link_ancestors ancestor->sample Always ancestor1->ancestor2 Only if ancestor2 has a relevant descendant sample1->sample2 Always sample->ancestor Only if ancestor has a relevant descendant

The difference between samples and ancestors is that information about the ancestors of a node in ancestors will only be retained if it also has a relevant descendant, while information about the ancestors of a node in samples will always be retained. The node IDs in parent and child refer to the IDs in the node table of the inputted tree sequence.

The supplied nodes must be non-empty lists of the node IDs in the tree sequence: in particular, they do not have to be samples of the tree sequence. The lists of samples and ancestors may overlap, although adding a node from samples to ancestors will not change the output. So, setting samples and ancestors to the same list of nodes will find all genealogical relationships within this list.

If none of the nodes in ancestors or samples are ancestral to samples anywhere in the tree sequence, an empty table will be returned.

Parameters
• samples (list[int]) – A list of node IDs to retain as samples.

• ancestors (list[int]) – A list of node IDs to use as ancestors.

Returns

An EdgeTable instance displaying relationships between the samples and ancestors.

ltrim(record_provenance=True)[source]

Reset the coordinate system used in these tables, changing the left and right genomic positions in the edge table such that the leftmost edge now starts at position 0. This is identical to TreeSequence.ltrim() but acts in place to alter the data in this TableCollection.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

property metadata

The decoded metadata for this TableCollection.

property metadata_bytes

The raw bytes of metadata for this TableCollection

property metadata_schema

The tskit.MetadataSchema for this TableCollection.

property name_map

Returns a dictionary mapping table names to the corresponding table instances. For example, the returned dictionary will contain the key “edges” that maps to an EdgeTable instance.

property nbytes

Returns the total number of bytes required to store the data in this table collection. Note that this may not be equal to the actual memory footprint.

rtrim(record_provenance=True)[source]

Reset the sequence_length property so that the sequence ends at the end of the last edge. This is identical to TreeSequence.rtrim() but acts in place to alter the data in this TableCollection.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

simplify(samples=None, *, reduce_to_site_topology=False, filter_populations=True, filter_individuals=True, filter_sites=True, keep_unary=False, keep_unary_in_individuals=None, keep_input_roots=False, record_provenance=True, filter_zero_mutation_sites=None)[source]

Simplifies the tables in place to retain only the information necessary to reconstruct the tree sequence describing the given samples. This will change the ID of the nodes, so that the node samples[k] will have ID k in the result. The resulting NodeTable will have only the first len(samples) nodes marked as samples. The mapping from node IDs in the current set of tables to their equivalent values in the simplified tables is also returned as a numpy array. If an array a is returned by this function and u is the ID of a node in the input table, then a[u] is the ID of this node in the output table. For any node u that is not mapped into the output tables, this mapping will equal -1.

Tables operated on by this function must: be sorted (see TableCollection.sort()), have children be born strictly after their parents, and the intervals on which any node is a child must be disjoint. Other than this the tables need not satisfy remaining requirements to specify a valid tree sequence (but the resulting tables will).

This is identical to TreeSequence.simplify() but acts in place to alter the data in this TableCollection. Please see the TreeSequence.simplify() method for a description of the remaining parameters.

Parameters
• samples (list[int]) – A list of node IDs to retain as samples. They need not be nodes marked as samples in the original tree sequence, but will constitute the entire set of samples in the returned tree sequence. If not specified or None, use all nodes marked with the IS_SAMPLE flag. The list may be provided as a numpy array (or array-like) object (dtype=np.int32).

• reduce_to_site_topology (bool) – Whether to reduce the topology down to the trees that are present at sites. (Default: False).

• filter_populations (bool) – If True, remove any populations that are not referenced by nodes after simplification; new population IDs are allocated sequentially from zero. If False, the population table will not be altered in any way. (Default: True)

• filter_individuals (bool) – If True, remove any individuals that are not referenced by nodes after simplification; new individual IDs are allocated sequentially from zero. If False, the individual table will not be altered in any way. (Default: True)

• filter_sites (bool) – If True, remove any sites that are not referenced by mutations after simplification; new site IDs are allocated sequentially from zero. If False, the site table will not be altered in any way. (Default: True)

• keep_unary (bool) – If True, preserve unary nodes (i.e. nodes with exactly one child) that exist on the path from samples to root. (Default: False)

• keep_unary_in_individuals (bool) – If True, preserve unary nodes that exist on the path from samples to root, but only if they are associated with an individual in the individuals table. Cannot be specified at the same time as keep_unary. (Default: None, equivalent to False)

• keep_input_roots (bool) – Whether to retain history ancestral to the MRCA of the samples. If False, no topology older than the MRCAs of the samples will be included. If True the roots of all trees in the returned tree sequence will be the same roots as in the original tree sequence. (Default: False)

• record_provenance (bool) – If True, record details of this call to simplify in the returned tree sequence’s provenance information (Default: True).

• filter_zero_mutation_sites (bool) – Deprecated alias for filter_sites.

Returns

A numpy array mapping node IDs in the input tables to their corresponding node IDs in the output tables.

Return type

numpy.ndarray (dtype=np.int32)

sort(edge_start=0)[source]

Sorts the tables in place. This ensures that all tree sequence ordering requirements listed in the Valid tree sequence requirements section are met, as long as each site has at most one mutation (see below).

If the edge_start parameter is provided, this specifies the index in the edge table where sorting should start. Only rows with index greater than or equal to edge_start are sorted; rows before this index are not affected. This parameter is provided to allow for efficient sorting when the user knows that the edges up to a given index are already sorted.

The node, population and provenance tables are not affected by this method.

Edges are sorted as follows:

• time of parent, then

• parent node ID, then

• child node ID, then

• left endpoint.

Note that this sorting order exceeds the edge sorting requirements for a valid tree sequence. For a valid tree sequence, we require that all edges for a given parent ID are adjacent, but we do not require that they be listed in sorted order.

Individuals are sorted so that parents come before children, and the parent column remapped as required.

Sites are sorted by position, and sites with the same position retain their relative ordering.

Mutations are sorted by site ID, and within the same site are sorted by time. Those with equal or unknown time retain their relative ordering. This does not currently rearrange tables so that mutations occur after their mutation parents, which is a requirement for valid tree sequences.

Migrations are sorted by time, source, dest, left and node values. This defines a total sort order, such that any permutation of a valid migration table will be sorted into the same output order. Note that this sorting order exceeds the migration sorting requirements for a valid tree sequence, which only requires that migrations are sorted by time value.

Parameters

edge_start (int) – The index in the edge table where sorting starts (default=0; must be <= len(edges)).

subset(nodes, record_provenance=True, *, reorder_populations=None, remove_unreferenced=None)[source]

Modifies the tables in place to contain only the entries referring to the provided list of node IDs, with nodes reordered according to the order they appear in the list. See TreeSequence.subset() for a more detailed description.

Note: there are no sortedness requirements on the tables.

Parameters
• nodes (list) – The list of nodes for which to retain information. This may be a numpy array (or array-like) object (dtype=np.int32).

• record_provenance (bool) – Whether to record a provenance entry in the provenance table for this operation.

• reorder_populations (bool) – Whether to reorder the population table (default: True). If False, the population table will not be altered in any way.

• remove_unreferenced (bool) – Whether sites, individuals, and populations that are not referred to by any retained entries in the tables should be removed (default: True). See the description for details.

tree_sequence()[source]

Returns a TreeSequence instance with the structure defined by the tables in this TableCollection. If the table collection is not in canonical form (i.e., does not meet sorting requirements) or cannot be interpreted as a tree sequence an exception is raised. The sort() method may be used to ensure that input sorting requirements are met. If the table collection does not have indexes they will be built.

Returns

A TreeSequence instance reflecting the structures defined in this set of tables.

Return type

TreeSequence

trim(record_provenance=True)[source]

Trim away any empty regions on the right and left of the tree sequence encoded by these tables. This is identical to TreeSequence.trim() but acts in place to alter the data in this TableCollection.

Parameters

record_provenance (bool) – If True, add details of this operation to the provenance table in this TableCollection. (Default: True).

union(other, node_mapping, check_shared_equality=True, add_populations=True, record_provenance=True)[source]

Modifies the table collection in place by adding the non-shared portions of other to itself. To perform the node-wise union, the method relies on a node_mapping array, that maps nodes in other to its equivalent node in self or tskit.NULL if the node is exclusive to other. See TreeSequence.union() for a more detailed description.

Parameters
• other (TableCollection) – Another table collection.

• node_mapping (list) – An array of node IDs that relate nodes in other to nodes in self: the k-th element of node_mapping should be the index of the equivalent node in self, or tskit.NULL if the node is not present in self (in which case it will be added to self).

• check_shared_equality (bool) – If True, the shared portions of the table collections will be checked for equality.

• add_populations (bool) – If True, nodes new to self will be assigned new population IDs.

• record_provenance (bool) – Whether to record a provenance entry in the provenance table for this operation.

### Tables¶

The tables API provides an efficient way of working with and interchanging tree sequence data. Each table class (e.g, NodeTable, EdgeTable, SiteTable) has a specific set of columns with fixed types, and a set of methods for setting and getting the data in these columns. The number of rows in the table t is given by len(t). Each table supports accessing the data either by row or column.

To access the data in a column, we can use standard attribute access which will return a copy of the column data as a numpy array. To access the data in a row, say row number j in table t, simply use t[j]. The returned row has attributes allowing contents to be accessed by name, e.g. site_table[0].position, sites_table[0].ancestral_state, sites_table[0].metadata etc. Note that row contents cannot be changed. To create a new row with changed content, row objects have a replace method. For example:

>>> import tskit
>>> t = tskit.EdgeTable()
0
1
>>> print(t)
╔══╤══════════╤══════════╤══════╤═════╤════════╗
╠══╪══════════╪══════════╪══════╪═════╪════════╣
║0 │0.00000000│1.00000000│    10│   11│     b''║
║1 │1.00000000│2.00000000│     9│   11│     b''║
╚══╧══════════╧══════════╧══════╧═════╧════════╝
>>> len(t)
2
>>> t.left
array([ 0.,  1.])
>>> t.parent
array([10,  9], dtype=int32)
>>> t[0]
>>> t[-1]
>>> t[-1].right
2.0
EdgeTableRow(left=1.0, right=2.0, parent=9, child=4, metadata='A new edge')
>>>


Tables also support the pickle protocol, and so can be easily serialised and deserialised (for example, when performing parallel computations using the multiprocessing module).

>>> serialised = pickle.dumps(t)
>>> print(t2)
id      left            right           parent  child
0       0.00000000      1.00000000      10      11
1       1.00000000      2.00000000      9       11


However, pickling will not be as efficient as storing tables in the native format.

Tables support the equality operator == based on the data held in the columns:

>>> t == t2
True
>>> t is t2
False
2
>>> print(t2)
id      left            right           parent  child
0       0.00000000      1.00000000      10      11
1       1.00000000      2.00000000      9       11
2       0.00000000      1.00000000      2       3
>>> t == t2
False


### Text columns¶

As described in the Encoding ragged columns, working with variable length columns is somewhat more involved. Columns encoding text data store the encoded bytes of the flattened strings, and the offsets into this column in two separate arrays.

Consider the following example:

>>> t = tskit.SiteTable()
>>> print(t)
0       0.00000000      A
1       1.00000000      BB
2       2.00000000
3       3.00000000      CCC
>>> t[0]
>>> t[1]
>>> t[2]
>>> t[3]


Here we create a SiteTable and add four rows, each with a different ancestral_state. We can then access this information from each row in a straightforward manner. Working with the data in the columns is a little trickier, however:

>>> t.ancestral_state
array([65, 66, 66, 67, 67, 67], dtype=int8)
>>> t.ancestral_state_offset
array([0, 1, 3, 3, 6], dtype=uint32)
>>> tskit.unpack_strings(t.ancestral_state, t.ancestral_state_offset)
['A', 'BB', '', 'CCC']


Here, the ancestral_state array is the UTF8 encoded bytes of the flattened strings, and the ancestral_state_offset is the offset into this array for each row. The tskit.unpack_strings() function, however, is a convient way to recover the original strings from this encoding. We can also use the tskit.pack_strings() to insert data using this approach:

>>> a, off = tskit.pack_strings(["0", "12", ""])
>>> t.set_columns(position=[0, 1, 2], ancestral_state=a, ancestral_state_offset=off)
>>> print(t)
0       0.00000000      0
1       1.00000000      12
2       2.00000000


When inserting many rows with standard infinite sites mutations (i.e., ancestral state is “0”), it is more efficient to construct the numpy arrays directly than to create a list of strings and use pack_strings(). When doing this, it is important to note that it is the encoded byte values that are stored; by default, we use UTF8 (which corresponds to ASCII for simple printable characters).:

>>> t_s = tskit.SiteTable()
>>> m = 10
>>> a = ord("0") + np.zeros(m, dtype=np.int8)
>>> off = np.arange(m + 1, dtype=np.uint32)
>>> t_s.set_columns(position=np.arange(m), ancestral_state=a, ancestral_state_offset=off)
>>> print(t_s)
0       0.00000000      0
1       1.00000000      0
2       2.00000000      0
3       3.00000000      0
4       4.00000000      0
5       5.00000000      0
6       6.00000000      0
7       7.00000000      0
8       8.00000000      0
9       9.00000000      0
>>> t_s.ancestral_state
array([48, 48, 48, 48, 48, 48, 48, 48, 48, 48], dtype=int8)
>>> t_s.ancestral_state_offset
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10], dtype=uint32)


Here we create 10 sites at regular positions, each with ancestral state equal to “0”. Note that we use ord("0") to get the ASCII code for “0” (48), and create 10 copies of this by adding it to an array of zeros. We have done this for illustration purposes: it is equivalent (though slower for large examples) to do a, off = tskit.pack_strings(["0"] * m).

Mutations can be handled similarly:

>>> t_m = tskit.MutationTable()
>>> site = np.arange(m, dtype=np.int32)
>>> d, off = tskit.pack_strings(["1"] * m)
>>> node = np.zeros(m, dtype=np.int32)
>>> t_m.set_columns(site=site, node=node, derived_state=d, derived_state_offset=off)
>>> print(t_m)
id      site    node    derived_state   parent  metadata
0       0       0       1       -1
1       1       0       1       -1
2       2       0       1       -1
3       3       0       1       -1
4       4       0       1       -1
5       5       0       1       -1
6       6       0       1       -1
7       7       0       1       -1
8       8       0       1       -1
9       9       0       1       -1
>>>


### Binary columns¶

Columns storing binary data take the same approach as Text columns to encoding variable length data. The difference between the two is only raw bytes values are accepted: no character encoding or decoding is done on the data. Consider the following example where a table has no metadata_schema such that arbitrary bytes can be stored and no automatic encoding or decoding of objects is performed by the Python API and we can store and retrieve raw bytes. (See Metadata for details):

>>> t = tskit.NodeTable()
b'raw bytes'
b'\x80\x03}q\x00X\x01\x00\x00\x00xq\x01G?\xf1\x99\x99\x99\x99\x99\x9as.'
{'x': 1.1}
>>> print(t)
0       0       -1      0.00000000000000        cmF3IGJ5dGVz
1       0       -1      0.00000000000000        gAN9cQBYAQAAAHhxAUc/8ZmZmZmZmnMu
array([ 114,   97,  119,   32,   98,  121,  116,  101,  115, -128,    3,
125,  113,    0,   88,    1,    0,    0,    0,  120,  113,    1,
71,   63,  -15, -103, -103, -103, -103, -103, -102,  115,   46], dtype=int8)
array([ 0,  9, 33], dtype=uint32)


Here we add two rows to a NodeTable, with different metadata. The first row contains a simple byte string, and the second contains a Python dictionary serialised using pickle. We then show several different (and seemingly incompatible!) different views on the same data.

When we access the data in a row (e.g., t[0].metadata) we are returned a Python bytes object containing precisely the bytes that were inserted. The pickled dictionary is encoded in 24 bytes containing unprintable characters, and when we unpickle it using pickle.loads(), we obtain the original dictionary.

When we print the table, however, we see some data which is seemingly unrelated to the original contents. This is because the binary data is base64 encoded to ensure that it is print-safe (and doesn’t break your terminal). (See the Metadata section for more information on the use of base64 encoding.).

Finally, when we print the metadata column, we see the raw byte values encoded as signed integers. As for Text columns, the metadata_offset column encodes the offsets into this array. So, we see that the first metadata value is 9 bytes long and the second is 24.

The tskit.pack_bytes() and tskit.unpack_bytes() functions are also useful for encoding data in these columns.

### Table classes¶

This section describes the methods and variables available for each table class. For description and definition of each table’s meaning and use, see the table definitions.

class tskit.IndividualTable[source]

A table defining the individuals in a tree sequence. Note that although each Individual has associated nodes, reference to these is not stored in the individual table, but rather reference to the individual is stored for each node in the NodeTable. This is similar to the way in which the relationship between sites and mutations is modelled.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(flags=0, location=None, parents=None, metadata=None)[source]

Adds a new row to this IndividualTable and returns the ID of the corresponding individual. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• flags (int) – The bitwise flags for the new node.

• location (array-like) – A list of numeric values or one-dimensional numpy array describing the location of this individual. If not specified or None, a zero-dimensional location is stored.

• parents (array-like) – A list or array of ids of parent individuals. If not specified an empty array is stored.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added node.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(flags=None, location=None, location_offset=None, parents=None, parents_offset=None, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns in this IndividualTable. This allows many new rows to be added at once.

The flags array is mandatory and defines the number of extra individuals to add to the table. The parents and parents_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. The location and location_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• flags (numpy.ndarray, dtype=np.uint32) – The bitwise flags for each individual. Required.

• location (numpy.ndarray, dtype=np.float64) – The flattened location array. Must be specified along with location_offset. If not specified or None, an empty location value is stored for each individual.

• location_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the location array.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each individual.

• parents (numpy.ndarray, dtype=np.int32) – The flattened parents array. Must be specified along with parents_offset. If not specified or None, an empty parents array is stored for each individual.

• parents_offset – The offsets into the parents array.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_location(locations)[source]

Packs the specified list of location values and updates the location and location_offset columns. The length of the locations array must be equal to the number of rows in the table.

Parameters

locations (list) – A list of locations interpreted as numpy float64 arrays.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

packset_parents(parents)[source]

Packs the specified list of parent values and updates the parent and parent_offset columns. The length of the parents array must be equal to the number of rows in the table.

Parameters

parents (list) – A list of list of parent ids, interpreted as numpy int32 arrays.

set_columns(flags=None, location=None, location_offset=None, parents=None, parents_offset=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this IndividualTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The flags array is mandatory and defines the number of individuals the table will contain. The location and location_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. The parents and parents_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• flags (numpy.ndarray, dtype=np.uint32) – The bitwise flags for each individual. Required.

• location (numpy.ndarray, dtype=np.float64) – The flattened location array. Must be specified along with location_offset. If not specified or None, an empty location value is stored for each individual.

• location_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the location array.

• parents (numpy.ndarray, dtype=np.int32) – The flattened parents array. Must be specified along with parents_offset. If not specified or None, an empty parents array is stored for each individual.

• parents_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the parents array.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each individual.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.NodeTable[source]

A table defining the nodes in a tree sequence. See the definitions for details on the columns in this table and the tree sequence requirements section for the properties needed for a node table to be a part of a valid tree sequence.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
• time (numpy.ndarray, dtype=np.float64) – The array of time values.

• flags (numpy.ndarray, dtype=np.uint32) – The array of flags values.

• population (numpy.ndarray, dtype=np.int32) – The array of population IDs.

• individual (numpy.ndarray, dtype=np.int32) – The array of individual IDs that each node belongs to.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened array of binary metadata values. See Binary columns for more details.

• metadata_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the metadata column. See Binary columns for more details.

__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(flags=0, time=0, population=- 1, individual=- 1, metadata=None)[source]

Adds a new row to this NodeTable and returns the ID of the corresponding node. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• flags (int) – The bitwise flags for the new node.

• time (float) – The birth time for the new node.

• population (int) – The ID of the population in which the new node was born. Defaults to tskit.NULL.

• individual (int) – The ID of the individual in which the new node was born. Defaults to tskit.NULL.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added node.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(flags=None, time=None, population=None, individual=None, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns in this NodeTable. This allows many new rows to be added at once.

The flags, time and population arrays must all be of the same length, which is equal to the number of nodes that will be added to the table. The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• flags (numpy.ndarray, dtype=np.uint32) – The bitwise flags for each node. Required.

• time (numpy.ndarray, dtype=np.float64) – The time values for each node. Required.

• population (numpy.ndarray, dtype=np.int32) – The population values for each node. If not specified or None, the tskit.NULL value is stored for each node.

• individual (numpy.ndarray, dtype=np.int32) – The individual values for each node. If not specified or None, the tskit.NULL value is stored for each node.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(flags=None, time=None, population=None, individual=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this NodeTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The flags, time and population arrays must all be of the same length, which is equal to the number of nodes the table will contain. The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• flags (numpy.ndarray, dtype=np.uint32) – The bitwise flags for each node. Required.

• time (numpy.ndarray, dtype=np.float64) – The time values for each node. Required.

• population (numpy.ndarray, dtype=np.int32) – The population values for each node. If not specified or None, the tskit.NULL value is stored for each node.

• individual (numpy.ndarray, dtype=np.int32) – The individual values for each node. If not specified or None, the tskit.NULL value is stored for each node.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.EdgeTable[source]

A table defining the edges in a tree sequence. See the definitions for details on the columns in this table and the tree sequence requirements section for the properties needed for an edge table to be a part of a valid tree sequence.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
• left (numpy.ndarray, dtype=np.float64) – The array of left coordinates.

• right (numpy.ndarray, dtype=np.float64) – The array of right coordinates.

• parent (numpy.ndarray, dtype=np.int32) – The array of parent node IDs.

• child (numpy.ndarray, dtype=np.int32) – The array of child node IDs.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened array of binary metadata values. See Binary columns for more details.

• metadata_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the metadata column. See Binary columns for more details.

__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(left, right, parent, child, metadata=None)[source]

Adds a new row to this EdgeTable and returns the ID of the corresponding edge. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• left (float) – The left coordinate (inclusive).

• right (float) – The right coordinate (exclusive).

• parent (int) – The ID of parent node.

• child (int) – The ID of child node.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added edge.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(left, right, parent, child, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns of this EdgeTable. This allows many new rows to be added at once.

The left, right, parent and child parameters are mandatory, and must be numpy arrays of the same length (which is equal to the number of additional edges to add to the table). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• left (numpy.ndarray, dtype=np.float64) – The left coordinates (inclusive).

• right (numpy.ndarray, dtype=np.float64) – The right coordinates (exclusive).

• parent (numpy.ndarray, dtype=np.int32) – The parent node IDs.

• child (numpy.ndarray, dtype=np.int32) – The child node IDs.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(left=None, right=None, parent=None, child=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this EdgeTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The left, right, parent and child parameters are mandatory, and must be numpy arrays of the same length (which is equal to the number of edges the table will contain). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• left (numpy.ndarray, dtype=np.float64) – The left coordinates (inclusive).

• right (numpy.ndarray, dtype=np.float64) – The right coordinates (exclusive).

• parent (numpy.ndarray, dtype=np.int32) – The parent node IDs.

• child (numpy.ndarray, dtype=np.int32) – The child node IDs.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

squash()[source]

Sorts, then condenses the table into the smallest possible number of rows by combining any adjacent edges. A pair of edges is said to be adjacent if they have the same parent and child nodes, and if the left coordinate of one of the edges is equal to the right coordinate of the other edge. The squash method modifies an EdgeTable in place so that any set of adjacent edges is replaced by a single edge. The new edge will have the same parent and child node, a left coordinate equal to the smallest left coordinate in the set, and a right coordinate equal to the largest right coordinate in the set. The new edge table will be sorted in the canonical order (P, C, L, R).

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.MigrationTable[source]

A table defining the migrations in a tree sequence. See the definitions for details on the columns in this table and the tree sequence requirements section for the properties needed for a migration table to be a part of a valid tree sequence.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
• left (numpy.ndarray, dtype=np.float64) – The array of left coordinates.

• right (numpy.ndarray, dtype=np.float64) – The array of right coordinates.

• node (numpy.ndarray, dtype=np.int32) – The array of node IDs.

• source (numpy.ndarray, dtype=np.int32) – The array of source population IDs.

• dest (numpy.ndarray, dtype=np.int32) – The array of destination population IDs.

• time (numpy.ndarray, dtype=np.float64) – The array of time values.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened array of binary metadata values. See Binary columns for more details.

• metadata_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the metadata column. See Binary columns for more details.

__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(left, right, node, source, dest, time, metadata=None)[source]

Adds a new row to this MigrationTable and returns the ID of the corresponding migration. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• left (float) – The left coordinate (inclusive).

• right (float) – The right coordinate (exclusive).

• node (int) – The node ID.

• source (int) – The ID of the source population.

• dest (int) – The ID of the destination population.

• time (float) – The time of the migration event.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added migration.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(left, right, node, source, dest, time, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns of this MigrationTable. This allows many new rows to be added at once.

All parameters except metadata and metadata_offset and are mandatory, and must be numpy arrays of the same length (which is equal to the number of additional migrations to add to the table). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• left (numpy.ndarray, dtype=np.float64) – The left coordinates (inclusive).

• right (numpy.ndarray, dtype=np.float64) – The right coordinates (exclusive).

• node (numpy.ndarray, dtype=np.int32) – The node IDs.

• source (numpy.ndarray, dtype=np.int32) – The source population IDs.

• dest (numpy.ndarray, dtype=np.int32) – The destination population IDs.

• time (numpy.ndarray, dtype=np.int64) – The time of each migration.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each migration.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(left=None, right=None, node=None, source=None, dest=None, time=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this MigrationTable using the values in the specified arrays. Overwrites any data currently stored in the table.

All parameters except metadata and metadata_offset and are mandatory, and must be numpy arrays of the same length (which is equal to the number of migrations the table will contain). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns. See Binary columns for more information and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• left (numpy.ndarray, dtype=np.float64) – The left coordinates (inclusive).

• right (numpy.ndarray, dtype=np.float64) – The right coordinates (exclusive).

• node (numpy.ndarray, dtype=np.int32) – The node IDs.

• source (numpy.ndarray, dtype=np.int32) – The source population IDs.

• dest (numpy.ndarray, dtype=np.int32) – The destination population IDs.

• time (numpy.ndarray, dtype=np.int64) – The time of each migration.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each migration.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.SiteTable[source]

A table defining the sites in a tree sequence. See the definitions for details on the columns in this table and the tree sequence requirements section for the properties needed for a site table to be a part of a valid tree sequence.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
• position (numpy.ndarray, dtype=np.float64) – The array of site position coordinates.

• ancestral_state (numpy.ndarray, dtype=np.int8) – The flattened array of ancestral state strings. See Text columns for more details.

• ancestral_state_offset (numpy.ndarray, dtype=np.uint32) – The offsets of rows in the ancestral_state array. See Text columns for more details.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened array of binary metadata values. See Binary columns for more details.

• metadata_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the metadata column. See Binary columns for more details.

__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(position, ancestral_state, metadata=None)[source]

Adds a new row to this SiteTable and returns the ID of the corresponding site. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• position (float) – The position of this site in genome coordinates.

• ancestral_state (str) – The state of this site at the root of the tree.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added site.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(position, ancestral_state, ancestral_state_offset, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns of this SiteTable. This allows many new rows to be added at once.

The position, ancestral_state and ancestral_state_offset parameters are mandatory, and must be 1D numpy arrays. The length of the position array determines the number of additional rows to add the table. The ancestral_state and ancestral_state_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Text columns for more information). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• position (numpy.ndarray, dtype=np.float64) – The position of each site in genome coordinates.

• ancestral_state (numpy.ndarray, dtype=np.int8) – The flattened ancestral_state array. Required.

• ancestral_state_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the ancestral_state array.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_ancestral_state(ancestral_states)[source]

Packs the specified list of ancestral_state values and updates the ancestral_state and ancestral_state_offset columns. The length of the ancestral_states array must be equal to the number of rows in the table.

Parameters

ancestral_states (list(str)) – A list of string ancestral state values.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(position=None, ancestral_state=None, ancestral_state_offset=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this SiteTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The position, ancestral_state and ancestral_state_offset parameters are mandatory, and must be 1D numpy arrays. The length of the position array determines the number of rows in table. The ancestral_state and ancestral_state_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Text columns for more information). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• position (numpy.ndarray, dtype=np.float64) – The position of each site in genome coordinates.

• ancestral_state (numpy.ndarray, dtype=np.int8) – The flattened ancestral_state array. Required.

• ancestral_state_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the ancestral_state array.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.MutationTable[source]

A table defining the mutations in a tree sequence. See the definitions for details on the columns in this table and the tree sequence requirements section for the properties needed for a mutation table to be a part of a valid tree sequence.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
• site (numpy.ndarray, dtype=np.int32) – The array of site IDs.

• node (numpy.ndarray, dtype=np.int32) – The array of node IDs.

• time (numpy.ndarray, dtype=np.float64) – The array of time values.

• derived_state (numpy.ndarray, dtype=np.int8) – The flattened array of derived state strings. See Text columns for more details.

• derived_state_offset (numpy.ndarray, dtype=np.uint32) – The offsets of rows in the derived_state array. See Text columns for more details.

• parent (numpy.ndarray, dtype=np.int32) – The array of parent mutation IDs.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened array of binary metadata values. See Binary columns for more details.

• metadata_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the metadata column. See Binary columns for more details.

__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(site, node, derived_state, parent=- 1, metadata=None, time=None)[source]

Adds a new row to this MutationTable and returns the ID of the corresponding mutation. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters
• site (int) – The ID of the site that this mutation occurs at.

• node (int) – The ID of the first node inheriting this mutation.

• derived_state (str) – The state of the site at this mutation’s node.

• parent (int) – The ID of the parent mutation. If not specified, defaults to NULL.

• metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

• time (float) – The occurrence time for the new mutation. If not specified, defaults to UNKNOWN_TIME, indicating the time is unknown.

Returns

The ID of the newly added mutation.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(site, node, derived_state, derived_state_offset, parent=None, time=None, metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns of this MutationTable. This allows many new rows to be added at once.

The site, node, derived_state and derived_state_offset parameters are mandatory, and must be 1D numpy arrays. The site and node (also time and parent, if supplied) arrays must be of equal length, and determine the number of additional rows to add to the table. The derived_state and derived_state_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Text columns for more information). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• site (numpy.ndarray, dtype=np.int32) – The ID of the site each mutation occurs at.

• node (numpy.ndarray, dtype=np.int32) – The ID of the node each mutation is associated with.

• time (numpy.ndarray, dtype=np.float64) – The time values for each mutation.

• derived_state (numpy.ndarray, dtype=np.int8) – The flattened derived_state array. Required.

• derived_state_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the derived_state array.

• parent (numpy.ndarray, dtype=np.int32) – The ID of the parent mutation for each mutation.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_derived_state(derived_states)[source]

Packs the specified list of derived_state values and updates the derived_state and derived_state_offset columns. The length of the derived_states array must be equal to the number of rows in the table.

Parameters

derived_states (list(str)) – A list of string derived state values.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(site=None, node=None, time=None, derived_state=None, derived_state_offset=None, parent=None, metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this MutationTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The site, node, derived_state and derived_state_offset parameters are mandatory, and must be 1D numpy arrays. The site and node (also parent and time, if supplied) arrays must be of equal length, and determine the number of rows in the table. The derived_state and derived_state_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Text columns for more information). The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• site (numpy.ndarray, dtype=np.int32) – The ID of the site each mutation occurs at.

• node (numpy.ndarray, dtype=np.int32) – The ID of the node each mutation is associated with.

• time (numpy.ndarray, dtype=np.float64) – The time values for each mutation.

• derived_state (numpy.ndarray, dtype=np.int8) – The flattened derived_state array. Required.

• derived_state_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the derived_state array.

• parent (numpy.ndarray, dtype=np.int32) – The ID of the parent mutation for each mutation.

• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.PopulationTable[source]

A table defining the populations referred to in a tree sequence. The PopulationTable stores metadata for populations that may be referred to in the NodeTable and MigrationTable”. Note that although nodes may be associated with populations, this association is stored in the NodeTable: only metadata on each population is stored in the population table.

Warning

The numpy arrays returned by table attribute accesses are copies of the underlying data. In particular, this means that you cannot edit the values in the columns by updating the attribute arrays.

NOTE: this behaviour may change in future.

Variables
__getitem__(index)

If passed an integer, return the specified row of this table, decoding metadata if it is present. Supports negative indexing, e.g. table[-5]. If passed a slice, iterable or array return a new table containing the specified rows. Similar to numpy fancy indexing, if the array or iterables contains booleans then the index acts as a mask, returning those rows for which the mask is True. Note that as the result is a new table, the row ids will change as tskit row ids are row indexes.

Parameters

index – the zero-index of a desired row, a slice of the desired rows, an iterable or array of the desired row numbers, or a boolean array to use as a mask.

add_row(metadata=None)[source]

Adds a new row to this PopulationTable and returns the ID of the corresponding population. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

metadata (object) – Any object that is valid metadata for the table’s schema. Defaults to the default metadata value for the table’s schema. This is typically {}. For no schema, None.

Returns

The ID of the newly added population.

Return type

int

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(metadata=None, metadata_offset=None)[source]

Appends the specified arrays to the end of the columns of this PopulationTable. This allows many new rows to be added at once.

The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_metadata=False)

Raise an AssertionError for the first found difference between this and another table of the same type.

Parameters
• other – Another table instance

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_metadata=False)

Returns True if self and other are equal. By default, two tables are considered equal if their columns and metadata schemas are byte-for-byte identical.

Parameters
• other – Another table instance

Returns

True if other is equal to this table; False otherwise.

Return type

bool

property metadata_schema

The tskit.MetadataSchema for this table.

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_metadata(metadatas)

Packs the specified list of metadata values and updates the metadata and metadata_offset columns. The length of the metadatas array must be equal to the number of rows in the table.

Parameters

set_columns(metadata=None, metadata_offset=None, metadata_schema=None)[source]

Sets the values for each column in this PopulationTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The metadata and metadata_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information) and Metadata for bulk table methods for an example of how to prepare metadata.

Parameters
• metadata (numpy.ndarray, dtype=np.int8) – The flattened metadata array. Must be specified along with metadata_offset. If not specified or None, an empty metadata value is stored for each node.

• metadata_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the metadata array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

class tskit.ProvenanceTable[source]

A table recording the provenance (i.e., history) of this table, so that the origin of the underlying data and sequence of subsequent operations can be traced. Each row contains a “record” string (recommended format: JSON) and a timestamp.

Todo

The format of the record field will be more precisely specified in the future.

Variables
• record (numpy.ndarray, dtype=np.int8) – The flattened array containing the record strings. Text columns for more details.

• record_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the record column. See Text columns for more details.

• timestamp (numpy.ndarray, dtype=np.int8) – The flattened array containing the timestamp strings. Text columns for more details.

• timestamp_offset (numpy.ndarray, dtype=np.uint32) – The array of offsets into the timestamp column. See Text columns for more details.

add_row(record, timestamp=None)[source]

Adds a new row to this ProvenanceTable consisting of the specified record and timestamp. If timestamp is not specified, it is automatically generated from the current time.

Parameters
• record (str) – A provenance record, describing the parameters and environment used to generate the current set of tables.

• timestamp (str) – A string timestamp. This should be in ISO8601 form.

append(row)

Adds a new row to this table and returns the ID of the new row. Metadata, if specified, will be validated and encoded according to the table’s metadata_schema.

Parameters

row (row-like) – An object that has attributes corresponding to the properties of the new row. Both the objects returned from table[i] and e.g. ts.individual(i) work for this purpose, along with any other object with the correct attributes.

Returns

The ID of the newly added node.

Return type

int

append_columns(timestamp=None, timestamp_offset=None, record=None, record_offset=None)[source]

Appends the specified arrays to the end of the columns of this ProvenanceTable. This allows many new rows to be added at once.

The timestamp and timestamp_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information). Likewise for the record and record_offset columns

Parameters
• timestamp (numpy.ndarray, dtype=np.int8) – The flattened timestamp array. Must be specified along with timestamp_offset. If not specified or None, an empty timestamp value is stored for each node.

• timestamp_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the timestamp array.

• record (numpy.ndarray, dtype=np.int8) – The flattened record array. Must be specified along with record_offset. If not specified or None, an empty record value is stored for each node.

• record_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the record array.

asdict()

Returns a dictionary mapping the names of the columns in this table to the corresponding numpy arrays.

assert_equals(other, *, ignore_timestamps=False)[source]

Raise an AssertionError for the first found difference between this and another provenance table.

Parameters
• other – Another provenance table instance

• ignore_timestamps (bool) – If True exclude the timestamp column from the comparison.

clear()

Deletes all rows in this table.

copy()

Returns a deep copy of this table

equals(other, ignore_timestamps=False)[source]

Returns True if self and other are equal. By default, two provenance tables are considered equal if their columns are byte-for-byte identical.

Parameters
• other – Another provenance table instance

• ignore_timestamps (bool) – If True exclude the timestamp column from the comparison.

Returns

True if other is equal to this provenance table; False otherwise.

Return type

bool

property nbytes

Returns the total number of bytes required to store the data in this table. Note that this may not be equal to the actual memory footprint.

packset_record(records)[source]

Packs the specified list of record values and updates the record and record_offset columns. The length of the records array must be equal to the number of rows in the table.

Parameters

records (list(str)) – A list of string record values.

packset_timestamp(timestamps)[source]

Packs the specified list of timestamp values and updates the timestamp and timestamp_offset columns. The length of the timestamps array must be equal to the number of rows in the table.

Parameters

timestamps (list(str)) – A list of string timestamp values.

set_columns(timestamp=None, timestamp_offset=None, record=None, record_offset=None)[source]

Sets the values for each column in this ProvenanceTable using the values in the specified arrays. Overwrites any data currently stored in the table.

The timestamp and timestamp_offset parameters must be supplied together, and meet the requirements for Encoding ragged columns (see Binary columns for more information). Likewise for the record and record_offset columns

Parameters
• timestamp (numpy.ndarray, dtype=np.int8) – The flattened timestamp array. Must be specified along with timestamp_offset. If not specified or None, an empty timestamp value is stored for each node.

• timestamp_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the timestamp array.

• record (numpy.ndarray, dtype=np.int8) – The flattened record array. Must be specified along with record_offset. If not specified or None, an empty record value is stored for each node.

• record_offset (numpy.ndarray, dtype=np.uint32.) – The offsets into the record array.

truncate(num_rows)

Truncates this table so that the only the first num_rows are retained.

Parameters

num_rows (int) – The number of rows to retain in this table.

### Table functions¶

tskit.parse_nodes(source, strict=True, encoding='utf8', base64_metadata=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of a node table and returns the corresponding NodeTable instance. See the node text format section for the details of the required format and the node table definition section for the required properties of the contents.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

• table (NodeTable) – If specified write into this table. If not, create a new NodeTable instance.

tskit.parse_edges(source, strict=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of a edge table and returns the corresponding EdgeTable instance. See the edge text format section for the details of the required format and the edge table definition section for the required properties of the contents.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• table (EdgeTable) – If specified, write the edges into this table. If not, create a new EdgeTable instance and return.

tskit.parse_sites(source, strict=True, encoding='utf8', base64_metadata=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of a site table and returns the corresponding SiteTable instance. See the site text format section for the details of the required format and the site table definition section for the required properties of the contents.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

• table (SiteTable) – If specified write site into this table. If not, create a new SiteTable instance.

tskit.parse_mutations(source, strict=True, encoding='utf8', base64_metadata=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of a mutation table and returns the corresponding MutationTable instance. See the mutation text format section for the details of the required format and the mutation table definition section for the required properties of the contents. Note that if the time column is missing its entries are filled with UNKNOWN_TIME.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

• table (MutationTable) – If specified, write mutations into this table. If not, create a new MutationTable instance.

tskit.parse_individuals(source, strict=True, encoding='utf8', base64_metadata=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of an individual table and returns the corresponding IndividualTable instance. See the individual text format section for the details of the required format and the individual table definition section for the required properties of the contents.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

• table (IndividualTable) – If specified write into this table. If not, create a new IndividualTable instance.

tskit.parse_populations(source, strict=True, encoding='utf8', base64_metadata=True, table=None)[source]

Parse the specified file-like object containing a whitespace delimited description of a population table and returns the corresponding PopulationTable instance. See the population text format section for the details of the required format and the population table definition section for the required properties of the contents.

See tskit.load_text() for a detailed explanation of the strict parameter.

Parameters
• source (io.TextIOBase) – The file-like object containing the text.

• strict (bool) – If True, require strict tab delimiting (default). If False, a relaxed whitespace splitting algorithm is used.

• encoding (str) – Encoding used for text representation.

• base64_metadata (bool) – If True, metadata is encoded using Base64 encoding; otherwise, as plain text.

• table (PopulationTable) – If specified write into this table. If not, create a new PopulationTable instance.

tskit.pack_strings(strings, encoding='utf8')[source]

Packs the specified list of strings into a flattened numpy array of 8 bit integers and corresponding offsets using the specified text encoding. See Encoding ragged columns for details of this encoding of columns of variable length data.

Parameters
• data (list[str]) – The list of strings to encode.

• encoding (str) – The text encoding to use when converting string data to bytes. See the codecs module for information on available string encodings.

Returns

The tuple (packed, offset) of numpy arrays representing the flattened input data and offsets.

Return type

numpy.ndarray (dtype=np.int8), numpy.ndarray (dtype=np.uint32)

tskit.unpack_strings(packed, offset, encoding='utf8')[source]

Unpacks a list of strings from the specified numpy arrays of packed byte data and corresponding offsets using the specified text encoding. See Encoding ragged columns for details of this encoding of columns of variable length data.

Parameters
• packed (numpy.ndarray) – The flattened array of byte values.

• offset (numpy.ndarray) – The array of offsets into the packed array.

• encoding (str) – The text encoding to use when converting string data to bytes. See the codecs module for information on available string encodings.

Returns

The list of strings unpacked from the parameter arrays.

Return type

list[str]

tskit.pack_bytes(data)[source]

Packs the specified list of bytes into a flattened numpy array of 8 bit integers and corresponding offsets. See Encoding ragged columns for details of this encoding.

Parameters

data (list[bytes]) – The list of bytes values to encode.

Returns

The tuple (packed, offset) of numpy arrays representing the flattened input data and offsets.

Return type

numpy.ndarray (dtype=np.int8), numpy.ndarray (dtype=np.uint32)

tskit.unpack_bytes(packed, offset)[source]

Unpacks a list of bytes from the specified numpy arrays of packed byte data and corresponding offsets. See Encoding ragged columns for details of this encoding.

Parameters
• packed (numpy.ndarray) – The flattened array of byte values.

• offset (numpy.ndarray) – The array of offsets into the packed array.

Returns

The list of bytes values unpacked from the parameter arrays.

Return type

## Constants¶

The following constants are used throughout the tskit API.

tskit.NULL = -1

Special reserved value representing a null ID.

tskit.NODE_IS_SAMPLE = 1

Node flag value indicating that it is a sample.

tskit.MISSING_DATA = -1

Special value representing missing data in a genotype array

tskit.FORWARD = 1

Constant representing the forward direction of travel (i.e., increasing genomic coordinate values).

tskit.REVERSE = -1

Constant representing the reverse direction of travel (i.e., decreasing genomic coordinate values).

tskit.ALLELES_ACGT = ('A', 'C', 'G', 'T')

The allele mapping where the four nucleotides A, C, G and T map to the genotype integers 0, 1, 2, and 3, respectively.

tskit.UNKNOWN_TIME = nan

Special NAN value used to indicate unknown mutation times. Since this is a NAN value, you cannot use == to test for it. Use is_unknown_time() instead.

The metadata module provides validation, encoding and decoding of metadata using a schema. See Metadata, Python Metadata API Overview and Working with Metadata.

class tskit.MetadataSchema(schema: Optional[Mapping[str, Any]])[source]

Class for validating, encoding and decoding metadata.

Parameters

schema (dict) – A dict containing a valid JSONSchema object.

asdict() → Optional[Mapping[str, Any]][source]

Returns a dict representation of this schema. One possible use of this is to modify this dict and then pass it to the MetadataSchema constructor to create a similar schema.

decode_row(row: bytes) → Any[source]

Decode an encoded row (bytes) of metadata, using the codec specifed in the schema and return a python dict. Note that no validation of the metadata against the schema is performed.

encode_row(row: Any)bytes[source]

Encode a row (dict) of metadata to its binary representation (bytes) using the codec specified in the schema. Note that unlike validate_and_encode_row() no validation against the schema is performed. This should only be used for performance if a validation check is not needed.

validate_and_encode_row(row: Any)bytes[source]

Validate a row (dict) of metadata against this schema and return the encoded representation (bytes) using the codec specified in the schema.

tskit.register_metadata_codec(codec_cls: Type[tskit.metadata.AbstractMetadataCodec], codec_id: str)None[source]

Register a metadata codec class. This function maintains a mapping from metadata codec identifiers used in schemas to codec classes. When a codec class is registered, it will replace any class previously registered under the same codec identifier, if present.

Parameters

codec_id (str) – String to use to refer to the codec in the schema.

## Combinatorics API¶

The combinatorics API deals with tree topologies, allowing them to be counted, listed and generated: see Combinatorics for a detailed description. Briefly, the position of a tree in the enumeration all_trees can be obtained using the tree’s rank() method. Inversely, a Tree can be constructed from a position in the enumeration with Tree.unrank(). Generated trees are associated with a new tree sequence containing only that tree for the entire genome (i.e. with num_trees = 1 and a sequence_length equal to the span of the tree).

tskit.all_trees(num_leaves, span=1)[source]

Generates all unique leaf-labelled trees with num_leaves leaves. See Combinatorics on the details of this enumeration. The leaf labels are selected from the set [0, num_leaves). The times and labels on internal nodes are chosen arbitrarily.

Parameters
• num_leaves (int) – The number of leaves of the tree to generate.

• span (float) – The genomic span of each returned tree.

Return type

tskit.Tree

tskit.all_tree_shapes(num_leaves, span=1)[source]

Generates all unique shapes of trees with num_leaves leaves.

Parameters
• num_leaves (int) – The number of leaves of the tree to generate.

• span (float) – The genomic span of each returned tree.

Return type

tskit.Tree

tskit.all_tree_labellings(tree, span=1)[source]

Generates all unique labellings of the leaves of a tskit.Tree. Leaves are labelled from the set [0, n) where n is the number of leaves of tree.

Parameters
• tree (tskit.Tree) – The tree used to generate labelled trees of the same shape.

• span (float) – The genomic span of each returned tree.

Return type

tskit.Tree

class tskit.TopologyCounter[source]

Contains the distributions of embedded topologies for every combination of the sample sets used to generate the TopologyCounter. It is indexable by a combination of sample set indexes and returns a collections.Counter whose keys are topology ranks (see Interpreting Tree Ranks). See Tree.count_topologies() for more detail on how this structure is used.

Note

This API will soon be deprecated in favour of multi-site extensions to the Statistics API.

class tskit.LdCalculator(tree_sequence)[source]

Class for calculating linkage disequilibrium coefficients between pairs of mutations in a TreeSequence. This class requires the numpy library.

This class supports multithreaded access using the Python threading module. Separate instances of LdCalculator referencing the same tree sequence can operate in parallel in multiple threads.

Note

This class does not currently support sites that have more than one mutation. Using it on such a tree sequence will raise a LibraryError with an “Unsupported operation” message.

Parameters

tree_sequence (TreeSequence) – The tree sequence containing the mutations we are interested in.

r2(a, b)[source]

Returns the value of the $$r^2$$ statistic between the pair of mutations at the specified indexes. This method is not an efficient method for computing large numbers of pairwise; please use either r2_array() or r2_matrix() for this purpose.

Parameters
• a (int) – The index of the first mutation.

• b (int) – The index of the second mutation.

Returns

The value of $$r^2$$ between the mutations at indexes a and b.

Return type

float

r2_array(a, direction=1, max_mutations=None, max_distance=None)[source]

Returns the value of the $$r^2$$ statistic between the focal mutation at index $$a$$ and a set of other mutations. The method operates by starting at the focal mutation and iterating over adjacent mutations (in either the forward or backwards direction) until either a maximum number of other mutations have been considered (using the max_mutations parameter), a maximum distance in sequence coordinates has been reached (using the max_distance parameter) or the start/end of the sequence has been reached. For every mutation $$b$$ considered, we then insert the value of $$r^2$$ between $$a$$ and $$b$$ at the corresponding index in an array, and return the entire array. If the returned array is $$x$$ and direction is tskit.FORWARD then $$x[0]$$ is the value of the statistic for $$a$$ and $$a + 1$$, $$x[1]$$ the value for $$a$$ and $$a + 2$$, etc. Similarly, if direction is tskit.REVERSE then $$x[0]$$ is the value of the statistic for $$a$$ and $$a - 1$$, $$x[1]$$ the value for $$a$$ and $$a - 2$$, etc.

Parameters
• a (int) – The index of the focal mutation.

• direction (int) – The direction in which to travel when examining other mutations. Must be either tskit.FORWARD or tskit.REVERSE. Defaults to tskit.FORWARD.

• max_mutations (int) – The maximum number of mutations to return $$r^2$$ values for. Defaults to as many mutations as possible.

• max_distance (float) – The maximum absolute distance between the focal mutation and those for which $$r^2$$ values are returned.

Returns

An array of double precision floating point values representing the $$r^2$$ values for mutations in the specified direction.

Return type

numpy.ndarray

Warning

For efficiency reasons, the underlying memory used to store the returned array is shared between calls. Therefore, if you wish to store the results of a single call to get_r2_array() for later processing you must take a copy of the array!

r2_matrix()[source]

Returns the complete $$m \times m$$ matrix of pairwise $$r^2$$ values in a tree sequence with $$m$$ mutations.

Returns

An 2 dimensional square array of double precision floating point values representing the $$r^2$$ values for all pairs of mutations.

Return type

numpy.ndarray

## Provenance¶

We provide some preliminary support for validating JSON documents against the provenance schema. Programmatic access to provenance information is planned for future versions.

tskit.validate_provenance(provenance)[source]

Validates the specified dict-like object against the tskit provenance schema. If the input does not represent a valid instance of the schema an exception is raised.

Parameters

provenance (dict) – The dictionary representing a JSON document to be validated against the schema.

Raises

tskit.ProvenanceValidationError

exception tskit.ProvenanceValidationError[source]

A JSON document did not validate against the provenance schema.

## Utility functions¶

Some top-level utility functions.

tskit.is_unknown_time(time)[source]

As the default unknown mutation time (UNKNOWN_TIME) is a specific NAN value, equality always fails (A NAN value is not equal to itself by definition). This method compares the bitfield such that unknown times can be detected. Either single floats can be passed or lists/arrays.

Note that NANs are a set of floating-point values. tskit.UNKNOWN_TIME is a specific value in this set. np.nan is a differing value, but both are NAN. See https://en.wikipedia.org/wiki/NaN

This function only returns true for tskit.is_unknown_time(tskit.UNKNOWN_TIME) and will return false for tskit.is_unknown_time(np.nan) or any other NAN or non-NAN value.

Parameters

time (Union[float, array-like]) – Value or array to check.

Returns

A single boolean or array of booleans the same shape as time.

Return type

Union[bool, numpy.ndarray[bool]]