What if I treated each item+pref-type as if they were separate items, separate dimensions? This would use weaker measures for user similarity along with strong purchase related prefs. But it avoids the problem of returning only recs for things with no expressed preference by the user in question. In fact I'd leave in the current filtering. I'd still get recs based on other item+pref-type dimensions but throwing them out and only returning item+purchase based recs would have the affect of filtering out things already purchased by the user.
Intuitively this seems to account for the affect: you looked at certain items and eventually purchased one and I looked at the same items so I might like what you purchased. It also seems to work better in the existing mahout framework. On Feb 9, 2013, at 11:50 AM, Pat Ferrel <[email protected]> wrote: I'd like to experiment with using several types of implicit preference values with recommenders. I have purchases as an implicit pref of high strength. I'd like to see if add-to-cart, view-product-details, impressions-seen, etc. can increase offline precision in holdout tests. These less than obvious implicit prefs will get a much lower value than purchase and i'll experiment with different mixes. The problem is that some of these prefs will indicate that the user, for whom I'm getting recs, has expressed a preference. Using these implicit prefs seems reasonable in finding similarity of taste between users but presents several problems. 1) how to encode the prefs, each impression-seen will increase the strength of preference of a user for an item but the recommender framework replaces the preference value for items preferred more than once, doesn't it? 2) AFAIK the current recommender framework will return recs only for items that the user in question has expressed no preference for. If I use something like view-product-details or impressions-seen, I will be removing anything the user has seen from the recs, which is not what I want in this experiment. Has anyone tried something like this? I'm not convinced that these other implicit preferences will add anything to the recommender, just trying to find out.
