I will think further but in the current implicit formulation with confidence, looks like I am factorizing a 0/1 matrix with weights 1 + alpha*rating for observed (1) values and 1 for unobserved (0) values. It's a bit different from LSA model.


On Sun, Jul 26, 2015 at 6:45 AM, Debasish Das <debasish.das83@gmail.com> wrote:
> Hi,
>
> Implicit factorization is important for us since it drives recommendation
> when modeling user click/no-click and also topic modeling to handle 0 counts
> in document x word matrices through NMF and Sparse Coding.
>
> I am a bit confused on this code:
>
> val c1 = alpha * math.abs(rating)
> if (rating > 0) ls.add(srcFactor, (c1 + 1.0)/c1, c1)
>
> When the alpha = 1.0 (high confidence) and rating is > 0 (true for word
> counts), why this formula does not become same as explicit formula:
>
> ls.add(srcFactor, rating, 1.0)
>
> For modeling document, I believe implicit Y'Y needs to stay but we need
> explicit ls.add(srcFactor, rating, 1.0)
>
> I am understanding confidence code further. Please let me know if the idea
> of mapping implicit to handle 0 counts in document word matrix makes sense.
>
> Thanks.
> Deb
>