A Generative Block-Diagonal Model for Clustering

Probabilistic mixture models are among the most important clustering methods. These models assume that the feature vectors of the samples can be described by a mixture of several components. Each of these components follows a distribution of a certain form. In recent years, there has been an increasing amount of interest and work in similarity-matrix-based methods. Rather than considering the feature vectors, these methods learn patterns by observing the similarity matrix that describes the pairwise relative similarity between each pair of samples. However, there are limited works in probabilistic mixture model for clustering with input data in the form of a similarity matrix. Observing this, we propose a generative model for clustering that finds the block-diagonal structure of the similarity matrix to ensure that the samples within the same cluster (diagonal block) are similar while the samples from different clusters (off-diagonal block) are less similar. In this model, we assume the elements in the similarity matrix follow one of beta distributions, depending on whether the element belongs to one of the diagonal blocks or to off-diagonal blocks. The assignment of the element to a block is determined by the cluster indicators that follow categorical distributions. Experiments on both synthetic and real data show that the performance of the proposed method is comparable to the state-of-the-art methods.