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From Sean Owen <sro...@gmail.com>
Subject Re: SVDRecommender
Date Tue, 21 Sep 2010 15:01:30 GMT
On Tue, Sep 21, 2010 at 3:53 PM, James James
<recommendersystem@yahoo.com> wrote:
>
> Hi,
>
> I was looking at the implementation of the SVDRecommender, and was wondering if
> anyone could point me to a paper or an algorithm on which the implementation is
> based.

This was asked recently on the mailing list, and all I knew was:
I'm not the author, but understand that the implementation is based on
an expectation maximization approach. I don't know the best resource,
nor the one that might have informed the implementation, but I suspect
this is basically it:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.68.1154&rep=rep1&type=pdf

>
> In addition, I was wondering if the current implementation supports
> binary-rating data (all we know is whether a piece of content is consumed or
> not).

You specifically mean the SVD implementation?
Sure you can feed in 1 and 0 and see the result (which will not be 1
and 0). It's not the most usual application for an SVD and I've never
done it.


> The current implementation relies on a value which is the average score given by
> all the users to all the items. In case of binary-rating data, there are no
> explicit scores given. However, if we assign 1 to all consumed items and 0 to
> all unconsumed items, we will be able to get an average score needed. Has
> anybody tried the SVDRecommender on such binary-rating data before?

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