In case somebody runs into the same situation, the key seems to be in the CandidateItemStrategy being passed to the constructor of GenericItemBasedRecommender. Looking into the code, if no CandidateItemStrategy is specified in the constructor, PreferredItemsNeighborhoodCandidateItemsStrategy is used and as the documentation says, the doGetCandidateItems method: "returns all items that have not been rated by the user and that were preferred by another user that has preferred at least one item that the current user has preferred too".
So, a different CandidateItemStrategy needs to be passed. For this problem, it seems to me that AllSimilarItemsCandidateItemsStrategy, AllUnknownItemsCandidateItemsStrategy are good candidates. Does anybody know where to find some documentation about the different CandidateItemStrategy? Based on the name I would say that: 1) AllSimilarItemsCandidateItemsStrategy returns all similar items regardless of whether they have been already rated by someone or not. 2) AllUnknownItemsCandidateItemsStrategy returns all similar items that have not been rated by anyone yet. Does anybody know if it works like that? Thanks. On Tue, Mar 4, 2014 at 9:16 AM, Juan José Ramos <jjar...@gmail.com> wrote: > First thing is thatI know this requirement would not make sense in a CF > Recommender. In my case, I am trying to use Mahout to create something > closer to a Content-Based Recommender. > > In particular, I am pre-computing a similarity matrix between all the > documents (items) of my catalogue and using that matrix as the > ItemSimilarity for my Item-Based Recommender. > > So, when a user rates a document, how could I make the recommender outputs > similar documents to that ones the user has already rated even if no other > user in the system has rated them yet? Is that even possible in the first > place? > > Thanks a lot. >
