Multi-class linear feature extraction by nonlinear PCA

The traditional way to find a linear solution to feature extraction problems is based on the maximization of the class-between scatter over the class-within scatter (Fisher´s mapping). For the multi-class problem this is sub-optimal due to class conjunctions, even for the simple situation of normal distributed classes with identical covariance matrices. We propose a novel, equally fast method, based on nonlinear principal component analysis (PCA). Although still sub-optimal, it may avoid the class conjunction. The proposed method is experimentally compared with Fisher´s mapping and with a neural network based approach to nonlinear PCA. It appears to outperform the both methods