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Calculate duplicate read frequency and mark duplicate reads in PacBio BAMs.
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README.md
markdup.py

README.md

markdup.py

Purpose

This is yet another markdup tool (YAMT) that serves much the same purpose as Picard MarkDuplicates or samtools markdup -- flag reads that are likely the result of PCR amplification.

For each alignment in an aligned, sorted BAM, I store reference id, alignment start, alignment end, read quality (priority: rq tag, mean of quality string, or dropped if missing), number of passes (np tag, dropped if missing), query length, and the md5 hash of the query name.

Reads are classified as duplicate if:

  1. reference id matches
  2. alignment starts and ends within aln_wiggle bp
  3. read length is within len_wiggle %

I choose a single alignment to represent each set of duplicates by the following rules in descending priority:

  1. highest read quality
  2. highest number of passes
  3. lowest query name md5 hash

The duplicate read frequency is output to stdout. If --output <target> is specified, a BAM is written to <target> with duplicate reads flagged with the 0x400 bit.

Requirements

python2 >=2.7

pip install pysam pandas numpy

Usage

usage: markdup.py [-h] [--outBAM OUTBAM]
                  [--aln_wiggle ALN_WIGGLE]
                  [--len_wiggle LEN_WIGGLE]
                  inBAM

Reads with identical alignments within aln_wiggle on both ends
and with length within len_wiggle % are marked as duplicates.
Alignment with highest read quality, number of passes, and 
query name md5 hash (in that order) is chosen as primary.

positional arguments:
  inBAM                 aligned bam

optional arguments:
  -h, --help                show this help message and exit
  --outBAM OUTBAM           output bam
  --aln_wiggle ALN_WIGGLE   bp alignment wiggle at ends, default 2
  --len_wiggle LEN_WIGGLE   percent read len wiggle, default 10
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