Discriminant analysis and similarity measure

• Published in: Pattern recognition 2014-01, Vol.47 (1), p.359-367
• Main Author: Liu, Chengjun
• Format: Article
• Language: English
• Subjects: Applied sciences; Bayes decision rule; Bayesian analysis; Cosine similarity measure; Decision analysis; Discriminant analysis; Exact sciences and technology; Face recognition; Face Recognition Grand Challenge (FRGC); Image processing; Information, signal and communications theory; New similarity measure; Normalized correlation; Norms; Pattern recognition; Performance enhancement; Signal processing; Similarity; Telecommunications and information theory
• ISSN: 0031-3203; 1873-5142
• DOI: 10.1016/j.patcog.2013.06.023

The cosine similarity measure is often applied after discriminant analysis in pattern recognition. This paper first analyzes why the cosine similarity is preferred by establishing the connection between the cosine similarity based decision rule in the discriminant analysis framework and the Bayes decision rule for minimum error. The paper then investigates the challenges inherent of the cosine similarity and presents a new similarity that overcomes these challenges. The contributions of the paper are thus three-fold. First, the application of the cosine similarity after discriminant analysis is discovered to have its theoretical roots in the Bayes decision rule. Second, some inherent problems of the cosine similarity such as its inadequacy in addressing distance and angular measures are discussed. Finally, a new similarity measure, which overcomes the problems by integrating the absolute value of the angular measure and the lp norm (the distance measure), is presented to enhance pattern recognition performance. The effectiveness of the proposed new similarity measure in the discriminant analysis framework is evaluated using a large scale, grand challenge problem, namely, the Face Recognition Grand Challenge (FRGC) problem. Experimental results using 36,818 FRGC images on the most challenging FRGC experiment, the FRGC Experiment 4, show that the new similarity measure improves face recognition performance upon other popular similarity measures, such as the cosine similarity measure, the normalized correlation, and the Euclidean distance measure. •The connection between the cosine similarity and the Bayes decision rule.•Discuss some inherent challenges of the cosine similarity.•A new similarity measure that integrates both angular and distance measure.•Experiments on the FRGC version 2 database (36,818 images).