title: Pointwise mutual information on text
body: <p>I was wondering how one would calculate the pointwise mutual information for text classification. To be more exact, I want to classify tweets in categories. I have a dataset of tweets (which are annotated), and I have a dictionary per category of words which belong to that category. Given this information, how is it possible to calculate the PMI for each category per tweet, to classify a tweet in one of these categories.</p>