Homework 2

Due Tuesday, March 9th Tuesday, March 23rd

Download the questions here.

• The Reuters21578 dataset. Also available from the UCI Machine Learning Repository.
• The C source code of a Porter Stemmer. You can find implementations in other languages here.
• A list of english stop words.

• Question 3 uses LibLinear which is a good package for classification with linear models. You'll find a lot of information on the LibLinear web site. However a local copy of the Liblinear source code is available here. The archive contains an useful README file.

• Important new information (3/17): The homework asks for ROC curves for models trained with options -s 0 and -s 3. However the LibLinear software only outputs probabilities for the log loss (-s 0). In order to obtain scores for the hinge loss (-s 3), you need to use this modified version of the file "predict.c". Note that these scores are not probabilities. They are simply the output of the discriminant function, positive for one class, negative for the other class.

Download the solutions here.