  We establish the consistency of K-medoids in the context of metric spaces. We
start by proving that K-medoids is asymptotically equivalent to K-means
restricted to the support of the underlying distribution under general
conditions, including a wide selection of loss functions. This asymptotic
equivalence, in turn, enables us to apply the work of Parna (1986) on the
consistency of K-means. This general approach applies also to non-metric
settings where only an ordering of the dissimilarities is available. We
consider two types of ordinal information: one where all quadruple comparisons
are available; and one where only triple comparisons are available. We provide
some numerical experiments to illustrate our theory.
