Unsupervised pattern classification by neural networks

A neural network is applied to the unsupervised pattern classification approach. Given a set of data consisting of unlabeled samples from several classes, the task of unsupervised classification is to label every sample in the same class by the same symbol such that the data set is divided into several clusters. We consider the hypothesis that the data set is drawn from a finite mixture of Gaussian distributions. The network architecture is a two-layer feedforward type: the units of the first layer are Gaussians and each correspond to one component of the mixture. The output layer provides the probability density estimation of the mixture. The weighted competitive learning is used to estimate the mean vectors and the non-diagonal covariance matrices of the Gaussian units. The number of Gaussian units in the hidden layer is optimized by informational criteria. Some of the results are reported, and the performance of this approach is evaluated.