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Self-Organizing Maps: Stationary States, Metastability and Convergence Rate
Citation key Erwin1992c
Author Erwin, E. and Obermayer, K. and Schulten, K.
Pages 35 – 45
Year 1992
ISSN 0340-1200
DOI 10.1007/BF00201800
Journal Biological Cybernetics
Volume 67
Publisher Springer-Verlag
Abstract We investigate the effect of various types of neighborhood function on the convergence rates and the presence or absence of metastable stationary states of Kohonen\'s self-organizing feature map algorithm in one dimension. We demonstrate that the time necessary to form a topographic representation of the unit interval [0, 1] may vary over several orders of magnitude depending on the range and also the shape of the neighborhood function, by which the weight changes of the neurons in the neighborhood of the winning neuron are scaled. We will prove that for neighborhood functions which are convex on an interval given by the length of the Kohonen chain there exist no metastable states. For all other neighborhood functions, metastable states are present and may trap the algorithm during the learning process. For the widely-used Gaussian function there exists a threshold for the width above which metastable states cannot exist. Due to the presence or absence of metastable states, convergence time is very sensitive to slight changes in the shape of the neighborhood function. Fastest convergence is achieved using neighborhood functions which are \"convex\" over a large range around the winner neuron and yet have large differences in value at neighboring neurons.
Bibtex Type of Publication Selected:quantization
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