A two-stage balancing strategy based on data augmentation for imbalanced text sentiment classification

In practice, the class imbalance is prevalent in sentiment classification tasks, which is harmful to classifiers. Recently, over-sampling strategies based on data augmentation techniques have caught the eyes of researchers. They generate new samples by rewriting the original samples. Nevertheless, the samples to be rewritten are usually selected randomly, which means that useless samples may be selected, thus adding this type of samples. Based on this observation, we propose a novel balancing strategy for text sentiment classification. Our approach takes word replacement as foundation and can be divided into two stages, which not only can balance the class distribution of training set, but also can modify noisy data. In the first stage, we perform word replacement on specific samples instead of random samples to obtain new samples. According to the noise detection, the second stage revises the sentiment of noisy samples. Toward this aim, we propose an improved term weighting called TF-IGM-CW for imbalanced text datasets, which contributes to extracting the target rewritten samples and feature words. We conduct experiments on four public sentiment datasets. Results suggest that our method outperforms several other resampling methods and can be integrated with various classification algorithms easily.