The popular population genetic software 'Treemix' by 'Pickrell and Pritchard' (2012) <DOI:10.1371/journal.pgen.1002967> estimates the number of migration edges on a population tree. However, it can be difficult to determine the number of migration edges to include. Previously, it was customary to stop adding migration edges when 99.8% of variation in the data was explained, but 'OptM' automates this process using an ad hoc statistic based on the second-order rate of change in the log likelihood. 'OptM' also has added functionality for various threshold modeling to compare with the ad hoc statistic.
copied from cf-staging / r-optm