Duplicates are handled by over-writing. There's not a way to represent two states of a user-item association simultaneously. It could be an issue only if you made your own data splitter that didn't properly put stuff in one bucket or the other, but I don't know that this is the issue here.
You might just run through the debugger and see just why it's 0. Is it really predicting with perfect accuracy every time? how many times? what data points... may give a clue quickly about the issue. On Sun, Jul 15, 2012 at 4:23 PM, Matt Mitchell <[email protected]> wrote: > OK hmm, is it possible this could happen from duplicate > user/pref/score values in my data? How does Mahout handle duplicate > entries in data, whether in a load-once file or coming from a refresh? > > On Sun, Jul 15, 2012 at 4:01 AM, Sean Owen <[email protected]> wrote: >> This sounds like a target leak, like your test data is actually >> getting copied into the training data. >> >> On Sun, Jul 15, 2012 at 1:08 AM, Matt Mitchell <[email protected]> wrote: >>> One strange thing, and I'm going to dig through the MIA book tonight, >>> is that my user based recommendation evaluator returns 0.0 no matter >>> what I do. It's setup using PearsonCorrelationSimilarity, >>> NearestNUserNeighborhood(2), GenericUserBasedRecommender and the >>> AverageAbsoluteDifferenceRecommenderEvaluator. Also, my prefs do have >>> values, a range from 1 to 3.
