Conformal prediction based active learning by linear regression optimization

Abstract

Conformal prediction uses the degree of strangeness (nonconformity) of data instances to determine the confidence values of new predictions. We propose a conformal prediction based active learning algorithm, referred to as CPAL-LR, to improve the performance of pattern classification algorithms. CPAL-LR uses a novel query function that determines the relevance of unlabeled instances through the solution of a constrained linear regression model, incorporating uncertainty, diversity, and representativeness in the optimization problem. Furthermore, we present a nonconformity measure that produces reliable confidence values. CPAL-LR is implemented in conjunction with support vector machines, sparse coding algorithms, and convolutional networks. Experiments conducted on face and object recognition databases demonstrate that CPAL-LR improves the classification performance of a variety classifiers, outperforming previously proposed active learning techniques, while producing reliable confidence values.