A cost-sensitive three-way combination technique for ensemble learning in sentiment classification

Deep neural networks (DNN) have achieved remarkable results in sentiment classification. Some ensemble methods of DNN models and traditional feature-based models are proposed recently. However, to the best of our knowledge, most of the works use traditional ensemble combination techniques, e.g. voting and stacking, which are designed for weak base classifiers. So far many base classifiers, e.g. DNN, have been able to achieve good results in sentiment classification tasks, so there should be a new ensemble combination technique designed for strong base classifiers. To address this issue, we proposed a cost-sensitive combination technique using sequential three-way decisions (3WD), which is named S3WC. In S3WC, base classifiers are arranged in a linear arrangement, and a gate mechanism is constructed in each step to divide the objects into three groups, i.e., positive region, negative region and boundary region, which respectively correspond to acceptance, rejection and deferment in sequential 3WD. Each object is grouped by minimizing its total cost consisting of misclassification cost and time cost. The objects in boundary region require more information to decrease the misclassification cost, so they are reclassified by the subsequent base classifiers in order to obtain more information, while the time cost increases. In the experiment, we apply S3WC to DNN models and traditional feature-based models on five benchmark datasets, and compare its performance with traditional ensemble combination techniques. The experimental results show that S3WC outperforms any of its base classifiers in terms of classification accuracy, and the total cost of S3WC is lower than that of the existing ensemble combination techniques (e.g. majority-voting, weighted-voting, meta-learning). (C) 2018 Elsevier Inc. All rights reserved.