This work belongs to the field of sentiment analysis; in particular, to opinion and emotion classification using a lexicon-based approach. It solves several problems related to increasing the effectiveness of opinion classification. The first problem is related to lexicon labelling. Human labelling in the field of emotions is often too subjective and ambiguous, and so the possibility of replacement by automatic labelling is examined. This paper offers experimental results using a nature-inspired algorithm—particle swarm optimization—for labelling. This optimization method repeatedly labels all words in a lexicon and evaluates the effectiveness of opinion classification using the lexicon until the optimal labels for words in the lexicon are found. The second problem is that the opinion classification of texts which do not contain words from the lexicon cannot be successfully done using the lexicon-based approach. Therefore, an auxiliary approach, based on a machine learning method, is integrated into the method. This hybrid approach is able to classify more than 99% of texts and achieves better results than the original lexicon-based approach. The final hybrid model can be used for emotion analysis in human–robot interactions.

No abstract

No abstract

Nowadays, with enhancing possibilities of the Internet usage, the number of its users grows as well. People use it more and more to communicate among themselves. This kind of communication plays a significant role in the decision-making process. Based on this finding, a need to analyze the content of the ample web discussions (so-called conversational content) using the computers arose. Therefore, the following article deals especially with the issue of opinion analysis, more specifically the classification of opinions. We have created an algorithm, which allows determining the polarity of the text. With the analysis of text we can also process the intensification, negation and their combinations. We have created 4 classification dictionaries divided according to the types of words they contain. We have subsequently tested the algorithm with average accuracy of 86%.

Sentiment analysis in the minor languages, such as Slovak, using dictionary approach is a difficult task. It requires a lot of human effort and it is time-consuming to prepare a reliable source of information, especially good dictionary. We propose an approach which uses a biologically inspired algorithm to find optimal polarity values for sentimental words. It applies a swarm intelligence algorithms, standard Particle Swarm Optimization (PSO) and Bare-bones Particle Swarm Optimization (BBPSO), to replace a human annotator at the moment of dictionary creation. We created two dictionaries, which were annotated by the human annotator, PSO and BBPSO. These dictionaries were compared with the result that the versions annotated by PSO and BBPSO outperformed a human annotator. Then a combined approach was used to classify reviews that do not contain words from the dictionary. These reviews decrease the classification performance significantly. The combined approach implements machine learning method to build a model based on the reviews classified by the dictionary approach. The combined approach finally reduced a number of unclassified reviews from 18% and 40.2% to 0.3% and increased the macro-F1 measure from 0.694 and 0.495 to 0.865 and 0.841.