Maximum margin tree error correcting output codes

Abstract

Encoding is one of the most important steps in Error Correcting Output Codes (ECOCs). Traditional encoding strategies are usually data-independent. Recently, some tree-form encoding algorithms are proposed which firstly utilize mutual information to estimate inter-class separability in order to create a hierarchical partition of the tree from top to down and then obtain a coding matrix. But such criterion is usually computed by a non-parametric method which would generally require vast samples and is more likely to lead to unstable results. In this paper, we present a novel encoding algorithm which uses the maximum margins between classes as the criterion and constructs a bottom-up binary tree based on the maximum margin. As a result, the corresponding coding matrix is more stable and discriminative for the following classification. Experimental results have shown that our algorithm performs much better than some state-of-the-art coding algorithms in ECOC.