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samtools-calmd(1)	     Bioinformatics tools	     samtools-calmd(1)

NAME
       samtools	calmd -	calculates MD and NM tags

SYNOPSIS
       samtools	calmd [-Eeubr] [-C capQcoef] aln.bam ref.fasta

DESCRIPTION
       Generate	 the  MD  tag.	If the MD tag is already present, this command
       will give a warning if the MD tag generated is different	from  the  ex-
       isting tag. Output SAM by default.

       Calmd  can  also	read and write CRAM files although in most cases it is
       pointless as CRAM recalculates MD and NM	tags on	the fly.  The one  ex-
       ception	to  this  case	is where both input and	output CRAM files have
       been / are being	created	with the no_ref	option.

       Note that some aligners do not include sequence or confidence values in
       secondary and supplementary alignment records.  Where this  happens  in
       SAM  files,  a  "*" character will be seen in the SEQ and QUAL columns.
       These records will be skipped, as it is not possible to recalculate the
       MD and NM tags without access to	the query  sequence.   samtools	 calmd
       will emit a warning if any records have been skipped for	this reason.

       Calmd  works  best on position-sorted input files, as with these	it can
       stream through the reference sequence and so doesn't have to store much
       reference data at any one time.	For other orderings, it	 may  have  to
       switch to a caching mode	which keeps the	reference sequences in memory.
       This will result	in calmd using more memory (up to the full size	of the
       reference)  than	 it would in the position-sorted case.	Note also that
       versions	of samtools calmd up to	1.16.1 should only be used on position
       sorted inputs as	they could be very slow	when run on other orderings.

OPTIONS
       -A      When used jointly with -r this option overwrites	 the  original
	       base quality.

       -e      Convert	a the read base	to = if	it is identical	to the aligned
	       reference base. Indel caller does not support the  =  bases  at
	       the moment.

       -u      Output uncompressed BAM

       -b      Output compressed BAM

       -C INT  Coefficient  to cap mapping quality of poorly mapped reads. See
	       the mpileup command for details.	[0]

       -r      Compute the BQ tag (without -A) or  cap	base  quality  by  BAQ
	       (with -A).

       -E      Extended	 BAQ  calculation.  This option	trades specificity for
	       sensitivity, though the effect is minor.

       --no-PG Do not add a @PG	line to	the header of the output file.

       -@, --threads INT
	       Number of input/output compression threads to use  in  addition
	       to main thread [0].

EXAMPLES
       o Dump BAQ applied alignment for	other SNP callers:

	   samtools calmd -bAr aln.bam > aln.baq.bam

	 It  adds  and corrects	the NM and MD tags at the same time. The calmd
	 command also comes with the  -C  option,  the	same  as  the  one  in
	 mpileup.  Apply if it helps.

AUTHOR
       Written by Heng Li from the Sanger Institute.

SEE ALSO
       samtools(1), samtools-mpileup(1)

       Samtools	website: <http://www.htslib.org/>

samtools-1.21		       12 September 2024	     samtools-calmd(1)

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