Calculating coverage from ref and alt columns?

Question

[PsFeathers]

Forgive this beginner question...I'm a bit new to this.

I have what looks like a vcf file with some of the headers as: chr, pos, ref, alt, etc

I was asked to find the coverage by adding the ref and alt and finding the maximum value. But since the ref and alt columns aren't numeric, what do I add?

A table example is:

chr  ref    alt
7     G      A
7     G      A
7     G      A
7     A      G
7     A      G
7    GA      G

Do I count the number of occurences of lets say 'G' in the ref column...and then add them to the number of occurrences of 'G' in the alt column?

[GouthamAtla]

1. Its not a vcf looking like file. you do not have SNP position.
2. Do you want to find the coverage of ref and alt base from a BAM file ?

[jjaimi921129]

Sorry I am new to bioinformatics too... I have problem on getting mean coverage, I've tried 'bedtools coverage' and 'samtools pileup', but the outputs are per site or region. I was wondering how can I get just one value (say 70X) averaged depth for CDS regions.