title: Distance learning in discriminative vector quantization.
abstract: Discriminative vector quantization schemes such as learning vector quantization (LVQ) and extensions thereof offer efficient and intuitive classifiers based on the representation of classes by prototypes. The original methods, however, rely on the Euclidean distance corresponding to the assumption that the data can be represented by isotropic clusters. For this reason, extensions of the methods to more general metric structures have been proposed, such as relevance adaptation in generalized LVQ (GLVQ) and matrix learning in GLVQ. In these approaches, metric parameters are learned based on the given classification task such that a data-driven distance measure is found. In this letter, we consider full matrix adaptation in advanced LVQ schemes. In particular, we introduce matrix learning to a recent statistical formalization of LVQ, robust soft LVQ, and we compare the results on several artificial and real-life data sets to matrix learning in GLVQ, a derivation of LVQ-like learning based on a (heuristic) cost function. In all cases, matrix adaptation allows a significant improvement of the classification accuracy. Interestingly, however, the principled behavior of the models with respect to prototype locations and extracted matrix dimensions shows several characteristic differences depending on the data sets.
authors.affiliation: Institute of Mathematics and Computing Science, University of Groningen, 9700 AK Groningen, The Netherlands. p.schneider@rug.nl
authors.forename: Petra
authors.initials: P
authors.lastname: Schneider
authors.forename: Michael
authors.initials: M
authors.lastname: Biehl
authors.forename: Barbara
authors.initials: B
authors.lastname: Hammer
mesh_terms: D000465:Algorithms; D000818:Animals; D001185:Artificial Intelligence; D001921:Brain / Q000502:physiology; D003198:Computer Simulation; D006801:Humans; D007858:Learning / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D016571:Neural Networks, Computer; D017711:Nonlinear Dynamics