Boundaries for simulated ancestry proportions when there are 3 ancestral populations. Figure 5a shows 4 valid regions, and if one decides to assign ethnicity according to the maximum value of the vector (adx1, adx2, adx3), it is not exactly clear what the correct ethnicity assignment should be for the individuals whose ancestry proportions fall in region IV. There is no such ambiguity in figure 5b.
Divers et al. BMC Genetics 2011 12:28 doi:10.1186/1471-2156-12-28