Black and white figure of kmeans clusters for subtype B sequences of the HIV protease. The figure displays the different mutation patterns characterizing each subtype B protease cluster. The columns in the figure represent the amino acid positions selected to the clustering and the rows, the protein sequences. Blue lines delimit the six classes, the black pixels represent mutations and the white pixels the absence of mutations. The number identifying each cluster is on the left and the number of the sequences in the cluster on the right.