Unsupervised Learning and Text Mining of Emotion Terms Using R

Unsupervised learning refers to data science approaches that involve learning without a prior knowledge about the classification of sample data. In Wikipedia, unsupervised learning has been described as "the task of inferring a function to describe hidden structure from'unlabeled' data (a classification of categorization is not included in the observations)". The overarching objectives of this post were to evaluate and understand the co-occurrence and/or co-expression of emotion words in individual letters, and if there were any differential expression profiles /patterns of emotions words among the 40 annual shareholder letters? Differential expression of emotion words was being used to refer to quantitative differences in emotion word frequency counts among letters, as well as qualitative differences in certain emotion words occurring uniquely in some letters but not present in others. This is the second part to a companion post I have on "parsing textual data for emotion terms".