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api.py
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api.py
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"""External API definitions."""
import warnings
import numpy as np
from .forward_backward.fb_diploid_variants_samples import (
backward_ls_dip_loop,
forward_ls_dip_loop,
)
from .forward_backward.fb_haploid_variants_samples import (
backwards_ls_hap,
forwards_ls_hap,
)
from .vit_diploid_variants_samples import (
backwards_viterbi_dip,
forwards_viterbi_dip_low_mem,
get_phased_path,
path_ll_dip,
)
from .vit_haploid_variants_samples import (
backwards_viterbi_hap,
forwards_viterbi_hap_lower_mem_rescaling,
path_ll_hap,
)
EQUAL_BOTH_HOM = 4
UNEQUAL_BOTH_HOM = 0
BOTH_HET = 7
REF_HOM_OBS_HET = 1
REF_HET_OBS_HOM = 2
MISSING_INDEX = 3
def check_alleles(alleles, m):
"""
Checks the specified allele list and returns a list of lists
of alleles of length num_sites.
If alleles is a 1D list of strings, assume that this list is used
for each site and return num_sites copies of this list.
Otherwise, raise a ValueError if alleles is not a list of length
num_sites.
"""
if isinstance(alleles[0], str):
return np.int8([len(alleles) for _ in range(m)])
if len(alleles) != m:
raise ValueError("Malformed alleles list")
n_alleles = np.int8([(len(alleles_site)) for alleles_site in alleles])
return n_alleles
def checks(
reference_panel,
query,
mutation_rate,
recombination_rate,
scale_mutation_based_on_n_alleles,
):
ref_shape = reference_panel.shape
ploidy = len(ref_shape) - 1
if ploidy not in (1, 2):
raise ValueError("Ploidy not supported.")
if not (query.shape[1] == ref_shape[0]):
raise ValueError(
"Number of variants in query does not match reference_panel. If haploid, ensure variant x sample matrices are passed."
)
if (ploidy == 2) and (not (ref_shape[1] == ref_shape[2])):
raise ValueError(
"reference_panel dimensions incorrect, perhaps a sample x sample x variant matrix was passed. Expected variant x sample x sample."
)
m = ref_shape[0]
n = ref_shape[1]
# Ensure that the mutation rate is either a scalar or vector of length m
if not isinstance(mutation_rate, float) and (mutation_rate is not None):
if type(mutation_rate is np.ndarray):
if mutation_rate.shape[0] is not m:
raise ValueError(
f"mutation_rate is not a scalar or vector of length m: {m}"
)
else:
raise ValueError(
f"mutation_rate is not a scalar or vector of length m: {m}"
)
# Ensure that the recombination probabilities is either a scalar or a vector of length m
if recombination_rate.shape[0] is not m:
raise ValueError(f"recombination_rate is not a vector of length m: {m}")
if isinstance(mutation_rate, float) and not (scale_mutation_based_on_n_alleles):
warnings.warn(
"Passed a scalar mutation rate, but not rescaling this mutation rate conditional on the number of alleles at the site"
)
if type(mutation_rate is np.ndarray) and (scale_mutation_based_on_n_alleles):
warnings.warn(
"Passed a vector of mutation rates, but rescaling each mutation rate conditional on the number of alleles at each site"
)
return n, m, ploidy
def set_emission_probabilities(
n,
m,
reference_panel,
query,
alleles,
mutation_rate,
ploidy,
scale_mutation_based_on_n_alleles,
):
# Check alleles should go in here, and modify e before passing to the algorithm
# If alleles is not passed, we don't perform a test of alleles, but set n_alleles based on the reference_panel.
if alleles is None:
n_alleles = np.int8(
[
len(np.unique(np.append(reference_panel[j, :], query[:, j])))
for j in range(reference_panel.shape[0])
]
)
else:
n_alleles = check_alleles(alleles, m)
if mutation_rate is None:
# Set the mutation rate to be the proposed mutation rate in Li and Stephens (2003).
theta_tilde = 1 / np.sum([1 / k for k in range(1, n - 1)])
mutation_rate = 0.5 * (theta_tilde / (n + theta_tilde))
if isinstance(mutation_rate, float):
mutation_rate = mutation_rate * np.ones(m)
if ploidy == 1:
# Haploid
# Evaluate emission probabilities here, using the mutation rate - this can take a scalar or vector.
e = np.zeros((m, 2))
if scale_mutation_based_on_n_alleles:
# Scale mutation based on the number of alleles - so the mutation rate is the mutation rate to one of the alleles.
# The overall mutation rate is then (n_alleles - 1) * mutation_rate.
e[:, 0] = mutation_rate - mutation_rate * np.equal(
n_alleles, np.ones(m)
) # Added boolean in case we're at an invariant site
e[:, 1] = 1 - (n_alleles - 1) * mutation_rate
else:
# No scaling based on the number of alleles - so the mutation rate is the mutation rate to anything.
# Which means that we must rescale the mutation rate to a different allele, by the number of alleles.
for j in range(m):
if n_alleles[j] == 1: # In case we're at an invariant site
e[j, 0] = 0
e[j, 1] = 1
else:
e[j, 0] = mutation_rate[j] / (n_alleles[j] - 1)
e[j, 1] = 1 - mutation_rate[j]
else:
# Diploid
# Evaluate emission probabilities here, using the mutation rate - this can take a scalar or vector.
# DEV: there's a wrinkle here.
e = np.zeros((m, 8))
e[:, EQUAL_BOTH_HOM] = (1 - mutation_rate) ** 2
e[:, UNEQUAL_BOTH_HOM] = mutation_rate ** 2
e[:, BOTH_HET] = (1 - mutation_rate) ** 2 + mutation_rate ** 2
e[:, REF_HOM_OBS_HET] = 2 * mutation_rate * (1 - mutation_rate)
e[:, REF_HET_OBS_HOM] = mutation_rate * (1 - mutation_rate)
e[:, MISSING_INDEX] = 1
return e
def viterbi_hap(n, m, reference_panel, query, emissions, recombination_rate):
V, P, log_likelihood = forwards_viterbi_hap_lower_mem_rescaling(
n, m, reference_panel, query, emissions, recombination_rate
)
most_likely_path = backwards_viterbi_hap(m, V, P)
return most_likely_path, log_likelihood
def viterbi_dip(n, m, reference_panel, query, emissions, recombination_rate):
V, P, log_likelihood = forwards_viterbi_dip_low_mem(
n, m, reference_panel, query, emissions, recombination_rate
)
unphased_path = backwards_viterbi_dip(m, V, P)
most_likely_path = get_phased_path(n, unphased_path)
return most_likely_path, log_likelihood
def forwards(
reference_panel,
query,
recombination_rate,
alleles=None,
mutation_rate=None,
scale_mutation_based_on_n_alleles=True,
):
"""
Run the Li and Stephens forwards algorithm on haplotype or
unphased genotype data.
"""
n, m, ploidy = checks(
reference_panel,
query,
mutation_rate,
recombination_rate,
scale_mutation_based_on_n_alleles,
)
emissions = set_emission_probabilities(
n,
m,
reference_panel,
query,
alleles,
mutation_rate,
ploidy,
scale_mutation_based_on_n_alleles,
)
if ploidy == 1:
forward_function = forwards_ls_hap
else:
forward_function = forward_ls_dip_loop
(
forward_array,
normalisation_factor_from_forward,
log_likelihood,
) = forward_function(
n, m, reference_panel, query, emissions, recombination_rate, norm=True
)
return forward_array, normalisation_factor_from_forward, log_likelihood
def backwards(
reference_panel,
query,
normalisation_factor_from_forward,
recombination_rate,
alleles=None,
mutation_rate=None,
scale_mutation_based_on_n_alleles=True,
):
"""
Run the Li and Stephens backwards algorithm on haplotype or
unphased genotype data.
"""
n, m, ploidy = checks(
reference_panel,
query,
mutation_rate,
recombination_rate,
scale_mutation_based_on_n_alleles,
)
emissions = set_emission_probabilities(
n,
m,
reference_panel,
query,
alleles,
mutation_rate,
ploidy,
scale_mutation_based_on_n_alleles,
)
if ploidy == 1:
backward_function = backwards_ls_hap
else:
backward_function = backward_ls_dip_loop
backwards_array = backward_function(
n,
m,
reference_panel,
query,
emissions,
normalisation_factor_from_forward,
recombination_rate,
)
return backwards_array
def viterbi(
reference_panel,
query,
recombination_rate,
alleles=None,
mutation_rate=None,
scale_mutation_based_on_n_alleles=True,
):
"""
Run the Li and Stephens Viterbi algorithm on haplotype or
unphased genotype data.
"""
n, m, ploidy = checks(
reference_panel,
query,
mutation_rate,
recombination_rate,
scale_mutation_based_on_n_alleles,
)
emissions = set_emission_probabilities(
n,
m,
reference_panel,
query,
alleles,
mutation_rate,
ploidy,
scale_mutation_based_on_n_alleles,
)
if ploidy == 1:
viterbi_function = viterbi_hap
else:
viterbi_function = viterbi_dip
most_likely_path, log_likelihood = viterbi_function(
n, m, reference_panel, query, emissions, recombination_rate
)
return most_likely_path, log_likelihood
def path_ll(
reference_panel,
query,
path,
recombination_rate,
alleles=None,
mutation_rate=None,
scale_mutation_based_on_n_alleles=True,
):
n, m, ploidy = checks(
reference_panel,
query,
mutation_rate,
recombination_rate,
scale_mutation_based_on_n_alleles,
)
emissions = set_emission_probabilities(
n,
m,
reference_panel,
query,
alleles,
mutation_rate,
ploidy,
scale_mutation_based_on_n_alleles,
)
if ploidy == 1:
path_ll_function = path_ll_hap
else:
path_ll_function = path_ll_dip
ll = path_ll_function(
n, m, reference_panel, path, query, emissions, recombination_rate
)
return ll