The 20 Newsgroups data set is a collection of approximately 20,000 newsgroup documents, partitioned (nearly) evenly across 20 different newsgroups. The data set can be downloaded here: . For simplicity, we will just focus on the "bag-of-words" representation of the documents given in the Matlab/Octave section. For example, the text file train.data is formatted "i j x" per line, meaning that in document i, term j appeared x times. The data has been divided into a training set and test set. You will build a model from the training set, and evaluate its performance on the test set