A Bayesian reassessment of nearest-neighbour classification

Lionel Cucala; Jean-Michel Marin; Christian Robert; Mike Titterington

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arXiv · 0802.1357

A Bayesian reassessment of nearest-neighbour classification

Lionel Cucala·Jean-Michel Marin·Christian Robert·Mike Titterington

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Abstract

The k-nearest-neighbour procedure is a well-known deterministic method used in supervised classification. This paper proposes a reassessment of this approach as a statistical technique derived from a proper probabilistic model; in particular, we modify the assessment made in a previous analysis of this method undertaken by Holmes and Adams (2002,2003), and evaluated by Manocha and Girolami (2007), where the underlying probabilistic model is not completely well-defined. Once a clear probabilistic basis for the k-nearest-neighbour procedure is established, we derive computational tools for conducting Bayesian inference on the parameters of the corresponding model. In particular, we assess the difficulties inherent to pseudo-likelihood and to path sampling approximations of an intractable normalising constant, and propose a perfect sampling strategy to implement a correct MCMC sampler associated with our model. If perfect sampling is not available, we suggest using a Gibbs sampling approximation. Illustrations of the performance of the corresponding Bayesian classifier are provided for several benchmark datasets, demonstrating in particular the limitations of the pseudo-likelihood approximation in this set-up.

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Lionel Cucala, Jean-Michel Marin, Christian Robert, Mike Titterington. 2008-02-10. A Bayesian reassessment of nearest-neighbour classification. https://arxiv.org/abs/0802.1357

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