Re-coding ECOCs without re-training

  • Authors:
  • Sergio Escalera;Oriol Pujol;Petia Radeva

  • Affiliations:
  • Centre de Visió per Computador, Campus UAB, Edifici O, Bellaterra, 08193 Barcelona, Spain and Dept. Matemítica Aplicada i Anílisi, Universitat de Barcelona, Gran Via 585, 08007 Barc ...;Centre de Visió per Computador, Campus UAB, Edifici O, Bellaterra, 08193 Barcelona, Spain and Dept. Matemítica Aplicada i Anílisi, Universitat de Barcelona, Gran Via 585, 08007 Barc ...;Centre de Visió per Computador, Campus UAB, Edifici O, Bellaterra, 08193 Barcelona, Spain and Dept. Matemítica Aplicada i Anílisi, Universitat de Barcelona, Gran Via 585, 08007 Barc ...

  • Venue:
  • Pattern Recognition Letters
  • Year:
  • 2010

Quantified Score

Hi-index 0.10

Visualization

Abstract

A standard way to deal with multi-class categorization problems is by the combination of binary classifiers in a pairwise voting procedure. Recently, this classical approach has been formalized in the Error-Correcting Output Codes (ECOC) framework. In the ECOC framework, the one-versus-one coding demonstrates to achieve higher performance than the rest of coding designs. The binary problems that we train in the one-versus-one strategy are significantly smaller than in the rest of designs, and usually easier to be learnt, taking into account the smaller overlapping between classes. However, a high percentage of the positions coded by zero of the coding matrix, which implies a high sparseness degree, does not codify meta-class membership information. In this paper, we show that using the training data we can redefine without re-training, in a problem-dependent way, the one-versus-one coding matrix so that the new coded information helps the system to increase its generalization capability. Moreover, the new re-coding strategy is generalized to be applied over any binary code. The results over several UCI Machine Learning repository data sets and two real multi-class problems show that performance improvements can be obtained re-coding the classical one-versus-one and Sparse random designs compared to different state-of-the-art ECOC configurations.