Annotating per-population MAC with +fill-tags

[alexpiper]

Hi bcftools team,

It would be very useful to have an option to annotate per-population minor allele count (MAC) in bcftools +fill-tags, analogous to the existing support for per-population tags such as MAF when using a sample-group file.

I was hoping to approximate MAC with a custom expression such as: bcftools +fill-tags in.bcf -- -S sample-group.txt -t 'MAC:1=int(MAF*AN)' but i can only manage to produce global MAC rather than population-specific MAC.

Is there a way to do this using custom expressions that I am missing, or could an official MAC tag be supported?

Thanks for your work on bcftools,
Alex