Feature Extraction for the k-Nearest Neighbour Classifier with Genetic Programming

  • Authors:
  • Martijn C. J. Bot

  • Affiliations:
  • -

  • Venue:
  • EuroGP '01 Proceedings of the 4th European Conference on Genetic Programming
  • Year:
  • 2001

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Abstract

In pattern recognition the curse of dimensionality can be handled either by reducing the number of features, e.g. with decision trees or by extraction of new features.We propose a genetic programming (GP) framework for automatic extraction of features with the express aim of dimension reduction and the additional aim of improving accuracy of the k-nearest neighbour (k-NN) classifier. We will show that our system is capable of reducing most datasets to one or two features while k-NN accuracy improves or stays the same. Such a small number of features has the great advantage of allowing visual inspection of the dataset in a two-dimensional plot.Since k-NN is a non-linear classification algorithm[2], we compare several linear fitness measures. We will show the a very simple one, the accuracy of the minimal distance to means (mdm) classifier outperforms all other fitness measures.We introduce a stopping criterion gleaned from numeric mathematics. New features are only added if the relative increase in training accuracy is more than a constant d, for the mdm classifier estimated to be 3.3%.