An example of two-way admixture from HapMap data.

The first two eigenvectors are shown for the four HapMap populations ASW, CEU, CHB, and YRI. A dispersion, or gradient, was formed by the ASW samples as a recently admixed population. CEU and YRI served as the proxy parental populations of ASW. CHB was included in the analysis to introduce an additional dimension of variation, so that the dispersion can be seen in the two-dimensional space. The third eigenvector addresses the within-population variation.