SOM of SOMs

  • Authors:
  • Tetsuo Furukawa

  • Affiliations:
  • Department of Brain Science and Engineering, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan

  • Venue:
  • Neural Networks
  • Year:
  • 2009

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Abstract

This paper proposes an extension of the self-organizing map (SOM), in which the mapping objects themselves are self-organizing maps. Thus a ''SOM of SOMs'' is presented, which we refer to as a SOM^2. A SOM^2 has a hierarchical structure consisting of a single parent SOM and a set of child SOMs. Each child SOM is trained to represent the distribution of a data class in a manifold, while the parent SOM generates a self-organizing map of the group of manifolds modeled by the child SOMs. Thus a SOM^2 is an architecture that organizes a product manifold represented as (child SOM) x (parent SOM). Such a product manifold is called a fiber bundle in terms of the topology. This extension of a SOM is easily generalized to any combination of SOM families, including cases of neural gas (NG) in which, for example, '' NG^2 (=NGxNG) as an NG of NGs'' and ''NGxSOM as a SOM of NGs'' are possible. Furthermore, a SOM^2 can be extended to a SOM^n, such as SOM^3=SOMxSOMxSOM defined as a ''SOM of SOM^2''. In this paper, the algorithms for the SOM^2 and its variations are introduced, and some simulation results are reported.