Robust parameter estimation for mixture model

An important problem in pattern recognition is the effect of limited training samples on classification performance. When the ratio of the number of training samples to the dimensionality is small, parameter estimates become highly variable, causing the deterioration of classification performance. This problem has become more prevalent in remote sensing with the emergence of a new generation of sensors. While the new sensor technology provides higher spectral and spatial resolution, enabling a greater number of spectrally separable classes to be identified, the needed labeled samples for designing the classifier remain difficult and expensive to acquire. Better parameter estimates can be obtained by exploiting a large number of unlabeled samples in addition to training samples using the expectation maximization (EM) algorithm under the mixture model. However, the estimation method is sensitive to the presence of statistical outliers. In remote sensing data, classes with few samples are difficult to identify and may constitute statistical outliers. Therefore, we propose a robust parameter estimation method for the mixture model. The proposed method assigns full weight to the sample from the main body of the data, but automatically gives reduced weight to statistical outliers. Experimental results show that the robust method prevents performance deterioration due to statistical outliers in the data as compared to the estimates obtained from EM approach.