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From Grant Ingersoll <>
Subject Re: Clarifying output from Taste demo
Date Fri, 20 Mar 2009 17:59:16 GMT

On Mar 20, 2009, at 1:48 PM, Sean Owen wrote:

> What do you mean by recommendations "given an item" -- I think the
> answer is 'yes' with a little work. Do you mean
> - recommended users that would like an item, given an item? Yes, this
> would mean transposing the data model so that user IDs are item IDs
> and vice versa, that's all
> - items similar to a given item? doesn't need a recommender, just use
> an ItemSimilarity. There is a convenience method on
> ItemBasedRecommender that does this for you too

Yes, this one, but the others are good to know, too.  I'm still a  
pretty new to CF, so bare w/ my dumb questions.   I was thinking I'd  
like to be able to do something like http://localhost:8080/mahout-taste-webapp/RecommenderServlet?itemID=15

  (instead of userId=?)

and it would give me back all the movies that are similar to movie 15.

> - recommendations from an "item-based recommender"? Sure just use
> GenericItemBasedRecommender. Indeed, the point of using this
> recommender is that you have some external, precomputed notion of item
> similarity (which makes things fast, and injects more information).
> But you can use a correlation-based similarity metric which is just
> based on preference values too. It works, just doesn't really exploit
> the point of item-based recommenders
> On Fri, Mar 20, 2009 at 5:10 PM, Grant Ingersoll  
> <> wrote:
>> Is there anyway in the demo to see item recommendations, given  
>> another item?
>>  I think my quick perusal of the code showed only userID as input,  
>> but maybe
>> I missed something.  BTW, that's item-item similarity, right?  And  
>> that is
>> usually calculated offline, right?

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