search for: demosntrates

Hi, I'm trying to generate a distance matrix between sample pairs (example below). I'm not very familiar with the loop command which I expect I will need for this. The example below demosntrates what I'd like to get out of the data - essentially, to calculate the proportion of positions where two samples differ. Any help much appreciated! Also, any notes on how the functions work would be great! Thanks! Example input (note: comma indicates column separators, a:d are sample names):...