BAF distribution of call sets. BAF distribution of different call sets. Box plots are drawn for BAF in true (pink boxes) and called somatic mutations. From low to high contamination, the mean BAF decreases from 50% to 5%. Due to the difficulty in finding low BAF mutations, the call sets show a slight to significant increase in BAF. Virmid with α calculates BAF closest to that of the true set. Due to the undetectable true somatic mutations that contain no B alleles, there can be a large gap between true and call set BAF distributions (α = 80% and 90%). BAF, B allele frequency.