How to combine chromosome vcf files
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6.1 years ago

Hi,

Easy question here. I am split up my vcf file up by chromosome to try and save some time. I want to combine the files now to have one complete vcf file with all the chromosomes. Do I wanted to merge the files or do I want to concatenate the files?

I just ran the command

cat *.vcf > cat.chr1.chr2.vcf

This was only on two of the chromosomes and when I went to look at the files, there was only data for the first chromosome and nothing for the second. Am I doing something wrong here? I could also try vcf tools if this "cat" command wont work for what I am trying to do.

Assembly alignment next-gen genome • 15k views
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10
Entering edit mode
6.1 years ago

first alternative, use one vcf file to get the header, and the concatenante all the other vcf without the header (this was your error)

grep '^#' chr1.vcf > merge.vcf
grep -v '^#' chr1.vcf  chr2.vcf chr3.vcf chr4.vcf   >> merge.vcf

second alternative: use picard gatherVcfs http://broadinstitute.github.io/picard/command-line-overview.html, which is going to check the headers, orders etc...

java -jar picard.jar GatherVcfs I=chr1.vcf  I=chr2.vcf I=chr3.vcf I=chr4.vcf  O=merged.vcf

update 2023:

use bcftools concat

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0
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Wonderful Pierre! Worked like a charm! Thank you so much for the help!

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Hi Pierre, I wanted to merge VCF files which had already splitted by chromosones into a single file. Though each is compressed i.e. chr1.vcf.gz, chr2.vcf.gz, ......chrn.vcf.gz.

I could not see any an output file merged.vcf.gz when I used the command. Is it because the file is compressed?

java -jar /programs/picard-tools-2.18.11/picard.jar GatherVcfs I=chr1.vcf.gz I=chr2.vcf.gz O=merged.vcf.gz
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Hi Pierre, do you know if it's possible to use GatherVCFs with a list of files rather than a separate I= for each? Thanks!

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1
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try to use a text file WITH THE SUFFIX .list containing the path to the files.

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