"""Supporting functions for the 'antitarget' command."""
from __future__ import absolute_import, division, print_function
import re
import sys
import logging
from Bio._py3k import range
iteritems = (dict.iteritems if sys.version_info[0] < 3 else dict.items)
from .params import INSERT_SIZE
from .rary import RegionArray as RA
[docs]def get_background(target_bed, access_bed, avg_bin_size, min_bin_size):
"""Generate background intervals from target intervals.
Procedure:
- Invert target intervals
- Subtract the inverted targets from accessible regions
- For each of the resulting regions:
- Shrink by a fixed margin on each end
- If it's smaller than min_bin_size, skip
- Divide into equal-size (region_size/avg_bin_size) portions
- Emit the (chrom, start, end) coords of each portion
"""
target_chroms = dict(RA.read(target_bed).by_chromosome())
if access_bed:
# Chromosome accessible sequence regions are given -- use them
access_chroms = dict(RA.read(access_bed).by_chromosome())
# But filter out untargeted allosomes/contigs
untgt_chroms = set(access_chroms) - set(target_chroms)
is_autosome = re.compile(r"(chr)?\d+$")
if any(is_autosome.match(c) for c in target_chroms):
# Autosomes have numeric names -- keep them
chroms_to_skip = [c for c in untgt_chroms
if not is_autosome.match(c)]
else:
# Alternative contigs have long names -- skip them
max_tgt_chr_name_len = max(map(len, target_chroms))
chroms_to_skip = [c for c in untgt_chroms
if len(c) > max_tgt_chr_name_len]
for untgt_chr in chroms_to_skip:
logging.info("Skipping untargeted chromosome %s", untgt_chr)
del access_chroms[untgt_chr]
else:
# Chromosome accessible sequence regions not known -- use heuristics
# (chromosome length is endpoint of last probe; skip initial
# <magic number> of bases that are probably telomeric)
TELOMERE_SIZE = 150000
access_chroms = guess_chromosome_regions(target_chroms, TELOMERE_SIZE)
backgrounds = find_background_regions(access_chroms, target_chroms,
2 * INSERT_SIZE)
bg_arr = RA.from_rows(backgrounds)
bg_arr.sort()
# Emit regions as antitarget bins according to avg_bin_size and min_bin_size
out_rows = []
for chrom, start, end in bg_arr.coords():
span = end - start
if span >= min_bin_size:
nbins = int(round(span / avg_bin_size)) or 1
if nbins == 1:
out_rows.append((chrom, start, end))
else:
# Divide the background region into equal-sized bins
bin_size = span / nbins
bin_start = start
bin_end = None
for i in range(1, nbins):
bin_end = start + int(i * bin_size)
out_rows.append((chrom, bin_start, bin_end))
bin_start = bin_end
out_rows.append((chrom, bin_start, end))
out_arr = RA.from_rows(out_rows)
out_arr["name"] = "Background"
return out_arr
[docs]def guess_chromosome_regions(target_chroms, telomere_size):
"""Determine (minimum) chromosome lengths from target coordinates."""
endpoints = [target_region[len(target_region) - 1, 'end']
for _chrom, target_region in target_chroms.iteritems()]
whole_chroms = RA.from_columns({"chromosome": target_chroms.keys(),
"start": telomere_size,
"end": endpoints})
return dict(whole_chroms.by_chromosome())
[docs]def find_background_regions(access_chroms, target_chroms, pad_size):
"""Take coordinates of accessible regions and targets; emit antitargets."""
for chrom, access_arr in access_chroms.iteritems():
if chrom in target_chroms:
target_regions = target_chroms[chrom].coords()
# Split each access_region at the targets it contains
_, tgt_start, tgt_end = next(target_regions)
assert tgt_start < tgt_end
for _, acc_start, acc_end in access_arr.coords():
if acc_end - acc_start <= 2 * pad_size:
# Accessible region is way too small
continue
bg_start = acc_start + pad_size
while tgt_start < acc_end:
# There may be at least one more target in this region
if tgt_end + pad_size > bg_start:
# Yes, there is a target in this region
if tgt_start - pad_size > bg_start:
# Split the background region at this target
yield (chrom, bg_start, tgt_start - pad_size)
bg_start = tgt_end + pad_size
# Done splitting that target; is there another?
try:
_, tgt_start, tgt_end = next(target_regions)
except StopIteration:
# Ensure all the remaining access_regions are unbroken
tgt_start = tgt_end = float('Inf')
# No remaining targets in this region - emit the rest of it
if acc_end - pad_size - bg_start > 0:
yield (chrom, bg_start, acc_end - pad_size)
else:
for _, acc_start, acc_end in access_arr.coords():
yield (chrom, acc_start + pad_size, acc_end - pad_size)