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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: ALS and SVD feature vectors
Date Wed, 04 Sep 2013 18:43:48 GMT
On Wed, Sep 4, 2013 at 10:59 AM, Dmitriy Lyubimov <dlieu.7@gmail.com> wrote:

> > Now, what happens in the case of SVD?
> > The vectors are normal by definition.
> > Are singular values used at all, or just left and right singular vectors?
>
> SVD does not take weights so it cannot ignore or weigh out a
> non-observation, which is why it is not well suited for matrix
> completion problem per se
>

There are multiple ways to read the use of weights here.

In the original posting, I think the gist was how to treat the singular
values, not how to weight different observations.  Mahout's SSVD allows the
singular values to be kept separate, to be applied entirely to the left or
right singular values or to be split across both in a square root sort of
way.

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