The supervised network self-organizing map for classification of large data sets

Stergios Papadimitriou, Seferina Mavroudi, Liviu Vladutu, G. Pavlides, Anastasios Bezerianos

Research output: Contribution to journalArticlepeer-review

Abstract

Complex application domains involve difficult pattern classification problems. The state space of these problems consists of regions that lie near class separation boundaries and require the construction of complex discriminants while for the rest regions the classification task is significantly simpler. The motivation for developing the Supervised Network Self-Organizing Map (SNet-SOM) model is to exploit this fact for designing computationally effective solutions. Specifically, the SNet-SOM utilizes unsupervised learning for classifying at the simple regions and supervised learning for the difficult ones in a two stage learning process. The unsupervised learning approach is based on the Self-Organizing Map (SOM) of Kohonen. The basic SOM is modified with a dynamic node insertion/deletion process controlled with an entropy based criterion that allows an adaptive extension of the SOM. This extension proceeds until the total number of training patterns that are mapped to neurons with high entropy (and therefore with ambiguous classification) reduces to a size manageable numerically with a capable supervised model. The second learning phase (the supervised training) has the objective of constructing better decision boundaries at the ambiguous regions. At this phase, a special supervised network is trained for the computationally reduced task of performing the classification at the ambiguous regions only. The performance of the SNet-SOM has been evaluated on both synthetic data and on an ischemia detection application with data extracted from the European ST-T database. In all cases, the utilization of SNet-SOM with supervised learning based on both Radial Basis Functions and Support Vector Machines has improved the results significantly related to those obtained with the unsupervised SOM and has enhanced the scalability of the supervised learning schemes. The highly disciplined design of the generalization performance of the Support Vector Machine allows to design the proper model for the particular training set.

Original languageEnglish (US)
Pages (from-to)185-203
Number of pages19
JournalApplied Intelligence
Volume16
Issue number3
DOIs
StatePublished - May 1 2002

Keywords

  • Computational complexity
  • Data mining
  • Divide and conquer algorithms
  • Ischemia detection
  • Learning vector quantization
  • Neural networks
  • Radial basis functions
  • Self-organizing maps
  • Support vector machines

ASJC Scopus subject areas

  • Artificial Intelligence

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