nltk/nltk — pull request #225 by apresta (2012-02-19 01:13:55+00:00)
Title: Positive Naive Bayes Classifier

An implementation of a "Positive Naive Bayes Classifier", introduced in

"Text Classification from Positive and Unlabeled Examples"
François Denis, Rémi Gilleron, Marc Tommasi (2002)
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.8.5291

The source contains a simple explanation.

An example application is the following: we want to highlight interesting articles for a user by looking at his click history. Clearly, a clicked article represents a positive example. However, an article that hasn't been clicked yet isn't necessarily a negative example. Still, the information that unlabeled examples give, together with positive-labeled ones, can help us build a naive bayes classifier for the task.
The only additional requirement is a prior distribution on the two labels (e.g., an estimate of how likely it is for an article to be interesting).