1. A system for clustering document collection observations, the system comprising: a processor; and a processor-readable storage medium in communication with the processor, wherein the processor-readable storage medium contains one or more programming instructions for: receiving a plurality of parameter vectors, determining a distribution, receiving a plurality of observations, wherein each observation corresponds to a document collection, selecting an optimal partitioning of the observations based on the distribution, the parameter vectors, and a likelihood function, and determining a cluster of observations based on the optimal partitioning.