Archetypal analysis represents each individual in a data set as a mixture of individuals of
pure type or archetypes. The archetypes themselves are restricted to being mixtures of the
individuals in the data set. Archetypes are selected by minimizing the squared error in
representing each individual as a mixture of archetypes. The usefulness of archetypal
analysis is illustrated on several data sets. Computing the archetypes is a nonlinear least
squares problem, which is solved using an alternating minimizing algorithm.