Swarm optimization clustering methods for opinion mining

Abstract

Opinion Mining (OM), also known as sentiment analysis, is the field of study that analyzes people’s sentiments, evaluations, attitudes, and emotions about different entities expressed in textual input. This is accomplished through the classification of an opinion into categories, such as positive, negative, or neutral. Supervised machine learning (ML) and lexicon-based are the most frequent approaches for OM. However, these approaches require considerable effort for preparing training data and to build the opinion lexicon, respectively. In order to address the drawbacks of these approaches, this Thesis proposes the use of unsupervised clustering approach for the OM task which is able to produce accurate results for several domains without manually labeled data for the training step or tools which are language dependent. Three swarm algorithms based on Particle Swarm Optimization (PSO) and Cuckoo Search (CS) are proposed: the DPSOMUT which is based on a discrete PSO binary version, the IDPSOMUT that is based on an Improved Self-Adaptive PSO algorithm with detection function, and the IDPSOMUT/CS that is a hybrid version of IDPSOMUT and CS. Several experiments were conducted with different corpora types, domains, text language, class balancing, fitness function, and pre-processing techniques. The effectiveness of the clustering algorithms was evaluated with external measures such as accuracy, precision, recall, and F-score. From the statistical analysis, it was possible to observe that the swarm-based algorithms, especially the PSO ones, were able to find better solutions than conventional grouping techniques, such as K-means and Agglomerative. The PSO-based algorithms achieved better accuracy using a word bigram pre-processing and the Global Silhouette as fitness function. The OBCC corpus is also another contribution of this Thesis and contains a gold collection with 2,940 tweets in Brazilian Portuguese with opinions of consumers about products and services.