18. The computer storage readable medium of claim 17 and further comprising: sequentially repeating the E-step and the M-step until clusters are identified that represent the observed data according to a predefined criteria.
17. A computer storage medium storing computer readable instructions which, when executed by a computer, cause the computer to perform steps comprising: performing an estimation-maximization (E-M) algorithm on observed data to identify cluster parameters indicative of hidden clusters in the observed data that represent the observed data, the E-M algorithm having an E-step in which the observed data is probabilistically divided into a first subset of the observed data that is represented, to a threshold level, by already defined clusters, and a second subset of the observed data that is not represented, to the threshold level, by the already defined clusters, the E-M algorithm having an M-step that identifies an additional cluster in the observed data, given the first and second subsets, that represents at least a portion of the observed data in the second subset at the threshold level; and adding the additional cluster to a model that includes the already defined clusters.