Analytic Comparison of Self-Organising Maps

  • Authors:
  • Rudolf Mayer;Robert Neumayer;Doris Baum;Andreas Rauber

  • Affiliations:
  • Vienna University of Technology, Austria;Norwegian University of Science and Technology, Norway;Fraunhofer Institute for Intelligent Analysis and Information Systems, Germany;Vienna University of Technology, Austria

  • Venue:
  • WSOM '09 Proceedings of the 7th International Workshop on Advances in Self-Organizing Maps
  • Year:
  • 2009

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Abstract

SOMs have proven to be a very powerful tool for data analysis. However, comparing multiple SOMs trained on the same data set using different parameters or initialisations is still a difficult task. In most cases it is performed only via visual inspection or by utilising one of a range of quality measures to compare vector quantisation or topology preservation characteristics of the maps. Yet, comparing SOMs systematically is both necessary as well as a powerful tool to further analyse data: necessary, because it may help to pick the most suitable SOM out of different training runs; a powerful tool because it allows analysing mapping stabilities across a range of parameter settings. In this paper we present an analytic approach to compare multiple SOMs trained on the same data set. Analysis of output space mapping, supported by a set of visualisations, reveals data co-locations and shifts on pairs of SOMs, considering both different neighbourhood sizes at source and target maps. A similar concept of mutual distances and relationships can be analysed at a cluster level. Finally, Comparisons aggregated automatically across several SOMs are strong indicators for strength and stability of mappings.