Large margin nearest neighbor classifiers

IEEE Trans Neural Netw. 2005 Jul;16(4):899-909. doi: 10.1109/TNN.2005.849821.

Abstract

The nearest neighbor technique is a simple and appealing approach to addressing classification problems. It relies on the assumption of locally constant class conditional probabilities. This assumption becomes invalid in high dimensions with a finite number of examples due to the curse of dimensionality. Severe bias can be introduced under these conditions when using the nearest neighbor rule. The employment of a locally adaptive metric becomes crucial in order to keep class conditional probabilities close to uniform, thereby minimizing the bias of estimates. We propose a technique that computes a locally flexible metric by means of support vector machines (SVMs). The decision function constructed by SVMs is used to determine the most discriminant direction in a neighborhood around the query. Such a direction provides a local feature weighting scheme. We formally show that our method increases the margin in the weighted space where classification takes place. Moreover, our method has the important advantage of online computational efficiency over competing locally adaptive techniques for nearest neighbor classification. We demonstrate the efficacy of our method using both real and simulated data.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Algorithms*
  • Artificial Intelligence*
  • Breast Neoplasms / diagnosis*
  • Computer Simulation
  • Computing Methodologies
  • Decision Support Techniques
  • Diabetes Mellitus / diagnosis*
  • Diagnosis, Computer-Assisted / methods*
  • Humans
  • Models, Biological*
  • Models, Statistical
  • Numerical Analysis, Computer-Assisted
  • Pattern Recognition, Automated / methods*
  • Stochastic Processes