Emotion space model for classifying opinions in stock message board

• We focus on the investors' opinion in stock message board.
• Extending six basic emotion words increases classifying accuracy.
• Opinion classifying based on ESM is effective and fast.
• We compare ESM with traditional SVM information gain and mutual information.

The online stock message is known to have impacts on the trend of the stock market. Understanding investor opinions in stock message boards is important, and the automatic classification of the investors’ opinions is one of the key methods for the issue. Traditional opinion classification methods mainly use terms and their frequency, part of speech, rule of opinions and sentiment shifters. But semantic information is ignored in term selection, and it is also hard to find the complete rules. In this paper, based on the classification of human emotions proposed by Ekman, we extend the traditional positive–negative analysis to the six important emotion states to build an extremely low dimensional emotion space model (ESM). It enables the prediction of investors’ emotions in public. Specifically, we use lexical semantic extension and correlation analysis methods to extend the scale of emotion words, which can capture more words with strong emotions for ad hoc domain, like network emotion symbols. We apply our ESM on messages of a famous stock message board TheLion. We also compare our model with traditional methods information gain and mutual information. The results show that ESM is not parameter sensitive. Besides, ESM is efficient for modeling sentiment classifying and can achieve higher classification accuracy than traditional ones.