Discriminative Semi-Supervised Dictionary Learning with Entropy Regularization for Pattern Classification

Dictionary learning has played an important role in the success of sparse representation, which triggers the rapid developments of unsupervised and supervised dictionary learning methods. However, in most practical applications, there are usually quite limited labeled training samples while it is relatively easy to acquire abundant unlabeled training samples. Thus semi-supervised dictionary learning that aims to effectively explore the discrimination of unlabeled training data has attracted much attention of researchers. Although various regularizations have been introduced in the prevailing semi-supervised dictionary learning, how to design an effective unified model of dictionary learning and unlabeled-data class estimating and how to well explore the discrimination in the labeled and unlabeled data are still open. In this paper, we propose a novel discriminative semi-supervised dictionary learning model (DSSDL) by introducing discriminative representation, an identical coding of unlabeled data to the coding of testing data final classification, and an entropy regularization term. The coding strategy of unlabeled data can not only avoid the affect of its incorrect class estimation, but also make the learned discrimination be well exploited in the final classification. The introduced regularization of entropy can avoid overemphasizing on some uncertain estimated classes for unlabeled samples. Apart from the enhanced discrimination in the learned dictionary by the discriminative representation, an extended dictionary is used to mainly explore the discrimination embedded in the unlabeled data. Extensive experiments on face recognition, digit recognition and texture classification show the effectiveness of the proposed method