Kernel mixture model for probability density estimation in Bayesian classifiers

Estimating reliable class-conditional probability is the prerequisite to implement Bayesian classifiers, and how to estimate the probability density functions (PDFs) is also a fundamental problem for other probabilistic induction algorithms. The finite mixture model (FMM) is able to represent arbitrary complex PDFs by using a mixture of mutimodal distributions, but it assumes that the component mixtures follows a given distribution, which may not be satisfied for real world data. This paper presents a non-parametric kernel mixture model (KMM) based probability density estimation approach, in which the data sample of a class is assumed to be drawn by several unknown independent hidden subclasses. Unlike traditional FMM schemes, we simply use the k-means clustering algorithm to partition the data sample into several independent components, and the regional density diversities of components are combined using the Bayes theorem. On the basis of the proposed kernel mixture model, we present a three-step Bayesian classifier, which includes partitioning, structure learning, and PDF estimation. Experimental results show that KMM is able to improve the quality of estimated PDFs of conventional kernel density estimation (KDE) method, and also show that KMM-based Bayesian classifiers outperforms existing Gaussian, GMM, and KDE-based Bayesian classifiers.