Comparison of feature extraction methods in dimensionality reduction

This technical note compares a number of feature extraction methods to determine which method enables higher accuracy of the performed classifications for dimensionality reduction in hyperspectral datasets. Two hyperspectral images were transformed into 10-, 15-, and 20-feature spaces using four unsupervised feature extraction methods (i.e., principal component analysis, maximum noise fraction, locally linear embedding (LLE), and independent component analysis) and one supervised feature extraction method (i.e., nonparametric weighted feature extraction, NWFE). A supervised classifier (i.e., support vector machine) processed a small number of training data and the feature spaces. The classification maps were compared with test samples, and then the classification accuracy of the feature extraction method was evaluated by kappa coefficient. With a 95% confidence interval of hypothesis testing, a 10-feature space could provide sufficient dimension for supervised classification and maximum noise fraction; and LLE outperformed the other feature extraction methods. Because NWFE might be limited by the small number of training samples, its classification performance was lower than those of the other feature extraction methods.