Remove substitutions that are more likely to be a result of ancient DNA damage (C->T and G->A substitutions).
keep_transitions(data, outfile = tempfile(fileext = ".snp"))
EIGENSTRAT data object.
Path to an output snp file with coordinates of excluded sites.
Updated S3 EIGENSTRAT data object with an additional 'exclude' slot specifying the path to the set of SNPs to be removed.