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:Date: 26 Jul 2016
:Author: Public Health England
"""Detect peaks in data based on their amplitude and other features."""
import argparse
from khmer import khmer_args
import khmer
from khmer.kfile import check_input_files
from khmer.khmer_args import build_counting_args
from scipy.signal import find_peaks_cwt
import sys
import numpy as np
def peakdet(v, delta, x=None):
Converted from MATLAB script at
Returns two arrays
function [maxtab, mintab]=peakdet(v, delta, x)
%PEAKDET Detect peaks in a vector
% [MAXTAB, MINTAB] = PEAKDET(V, DELTA) finds the local
% maxima and minima ("peaks") in the vector V.
% MAXTAB and MINTAB consists of two columns. Column 1
% contains indices in V, and column 2 the found values.
% With [MAXTAB, MINTAB] = PEAKDET(V, DELTA, X) the indices
% in MAXTAB and MINTAB are replaced with the corresponding
% X-values.
% A point is considered a maximum peak if it has the maximal
% value, and was preceded (to the left) by a value lower by
% Eli Billauer, 3.4.05 (Explicitly not copyrighted).
% This function is released to the public domain; Any use is allowed.
maxtab = []
mintab = []
if x is None:
x = np.arange(len(v))
v = np.asarray(v)
mn, mx = np.Inf, -np.Inf
mnpos, mxpos = np.NaN, np.NaN
lookformax = True
for i in np.arange(len(v)):
this = v[i]
if this > mx:
mx = this
mxpos = x[i]
if this < mn:
mn = this
mnpos = x[i]
if lookformax:
if this < mx - delta:
maxtab.append((mxpos, mx))
mn = this
mnpos = x[i]
lookformax = False
if this > mn + delta:
mintab.append((mnpos, mn))
mx = this
mxpos = x[i]
lookformax = True
maxtab = [ int(i[0]) for i in maxtab]
return maxtab
def plot(x, plot_file, min_peaks=None, max_peaks=None):
"""Plot results of the detect_peaks function, see its help."""
import matplotlib.pyplot as plt
except ImportError:
print('matplotlib is not available.')
_, ax = plt.subplots(1, 1, figsize=(8, 4))
ax.plot(x, 'black', lw=1)
if max_peaks:
ax.plot(max_peaks, x[max_peaks], '+', mfc=None, mec='g', mew=2, ms=8,
label='Max peaks')
if min_peaks:
ax.plot(min_peaks, x[min_peaks], '+', mfc=None, mec='r', mew=2, ms=8,
label='Min peaks')
ax.set_xlim(-.02 * x.size, x.size * 1.02 - 1)
ymin, ymax = x[np.isfinite(x)].min(), x[np.isfinite(x)].max()
yrange = ymax - ymin if ymax > ymin else 1
ax.set_ylim(ymin - 0.1 * yrange, ymax + 0.1 * yrange)
ax.set_xlabel('Abundance', fontsize=12)
ax.set_ylabel('Counts', fontsize=12)
ax.set_title("Min abundance finding.")
# plt.grid()
def get_args():
parser = build_counting_args(
descr="Calculate the abundance distribution of k-mers from a "
"single sequence file.")
parser.add_argument('input_sequence_filename', help='The name of the input'
' FAST[AQ] sequence file.')
parser.add_argument('-z', '--no-zero', dest='output_zero', default=True,
help='Do not output zero-count bins')
parser.add_argument('-b', '--no-bigcount', dest='bigcount', default=True,
help='Do not count k-mers past 255')
parser.add_argument('-s', '--squash', dest='squash_output', default=False,
help='Overwrite output file if it exists')
parser.add_argument('--savegraph', default='', metavar="filename",
help="Save the k-mer countgraph to the specified "
parser.add_argument('-f', '--force', default=False, action='store_true',
help='Overwrite output file if it exists')
parser.add_argument('-q', '--quiet', dest='quiet', default=False,
parser.add_argument('--max-abundance', default=300, type=int, help="Max abundance to consider.")
parser.add_argument('--hist-plot', help="If set, the histogram of process will be saved there.")
return parser
def main():
args = get_args().parse_args()
check_input_files(args.input_sequence_filename, args.force)
print('making countgraph')
countgraph = khmer_args.create_countgraph(args, multiplier=1.1)
print('building k-mer tracking graph')
tracking = khmer_args.create_nodegraph(args, multiplier=1.1)
print('kmer_size: %s' % countgraph.ksize())
print('k-mer countgraph sizes: %s' % countgraph.hashsizes())
# start loading
rparser = khmer.ReadParser(args.input_sequence_filename)
print('consuming input, round 1 -- %s' % args.input_sequence_filename)
print('Total number of unique k-mers: %s' %
abundance_lists = []
def __do_abundance_dist__(read_parser):
abundances = countgraph.abundance_distribution_with_reads_parser(
read_parser, tracking)
print('preparing hist from %s...' %
rparser = khmer.ReadParser(args.input_sequence_filename)
print('consuming input, round 2 -- %s' % args.input_sequence_filename)
assert len(abundance_lists) == 1, len(abundance_lists)
abundance = {}
for abundance_list in abundance_lists:
for i, count in enumerate(abundance_list):
abundance[i] = abundance.get(i, 0) + count
total = sum(abundance.values())
if 0 == total:
print("ERROR: abundance distribution is uniformly zero; "
"nothing to report.")
print("\tPlease verify that the input files are valid.")
return 1
np_abundance = np.zeros(len(abundance))
max_count = 0
sofar = 0
for row_i, count in sorted(abundance.items()):
if row_i == 0 and not args.output_zero:
np_abundance[row_i] = count
if count > max_count:
max_count = count
sofar += count
if sofar == total:
if args.max_abundance:
np_abundance = np_abundance[:args.max_abundance]
max_peaks = peakdet(np_abundance, 100)
min_peak = None
# Find lowest point in the interval
for valley in xrange(max_peaks[0], max_peaks[1]):
if min_peak is None:
min_peak = valley
elif np_abundance[valley] < np_abundance[min_peak]:
min_peak = valley
print min_peak if min_peak is not None else -1
result = 0
except IndexError:
sys.stderr.write("Could not estimate min abundance for %s.\n" % args.input_sequence_filename)
if len(max_peaks) <= 1:
sys.stderr.write("Is there enough data in the FastQ? Only %s peaks have been identified." % len(max_peaks))
result = 1
if args.hist_plot:
plot(np_abundance, args.hist_plot, max_peaks=max_peaks[0:2], min_peaks=min_peak)
return result
if __name__ == '__main__':

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@aunderwo aunderwo commented Jul 29, 2016



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@boydgreenfield boydgreenfield commented Jul 29, 2016

@alexjironkin: Very cool!! Quick question re: your testing -- have you experimented sub-sampling a FASTQ and then extrapolating back a min k-mer cutoff? (either just the head of a sample or a random subset of reads)

Curious as that would seem to open door to getting equivalent sketches from FASTQ subsets much faster.

Again, thanks for sharing!

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