AA/AB/BB Genotype information to Numeric

Question

[Emilie]

I have a file with just simple genotype information that has the individual, the SNP and the SNP designation in AA/AB/BB format (see below). For the program I want to use I need the SNPs represented in numeric form. What do I need in order to do that? What if I want to convert them to A,C,G,T format? I know they are from an Illumina chip.