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From Claudio Martella <>
Subject Re: item-based recommendation neighbourhood size
Date Sat, 20 Feb 2010 13:05:24 GMT
Sean Owen wrote:
> On Sat, Feb 20, 2010 at 12:46 PM, Claudio Martella
> <> wrote:
>> Can we rephrase jamborta's idea by saying that an item's neighboorhood
>> can be created by putting
>> "around" an item all those items that have been rated by the same users
>> with similar ratings?
> Yes, that's how I would define a neighborhood around anything: things
> that are similar / closest. "Similar" could indeed be based on user
> ratings (this is what PearsonCorrelationSimilarity does).
>> neighboorhood for items. What you can do now, is take your user's items
>> and see what's near them.
>> This is probably a rephrase of user-based recommendation, though.
> I wouldn't say you're describing user-based reocommendation. You've
> correctly described defining a neighborhood of similar items. This is
> how ItemBasedRecommender.mostSimilarItems() works, indeed.
> But that method is not computing recommendations.

Can't i recommend you the items around the items you like? why isn't it
computing recommendations?

>  And I thought the
> question was, why doesn't an item neighborhood enter into a
> recommender computation? It doesn't at the moment, and I mentioned
> above how it could, but why it might not help or be beneficial. But I
> haven't tried it.
> But yes maybe that remains the issue here... what's the question
> exactly about item neighborhoods? Their definition is clear; the use
> is not as much.

I agree.

Claudio Martella
Digital Technologies
Unit Research & Development - Analyst

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