R package protoclust: Hierarchical Clustering with Prototypes. Performs minimax linkage hierarchical clustering. Every cluster has an associated prototype element that represents that cluster as described in Bien, J., and Tibshirani, R. (2011), ”Hierarchical Clustering with Prototypes via Minimax Linkage,” accepted for publication in The Journal of the American Statistical Association, DOI: 10.1198/jasa.2011.tm10183.