On 04/06/10 08:53, Ted Dunning wrote:
On Fri, Jun 4, 2010 at 12:38 AM, Sean Owen<[email protected]> wrote:
They also add on the "row" average to make a prediction, which is the
average rating by the user, I'm guessing -- "row" is a row of A?
I would guess so, but that would only make sense if they subtracted it ahead
of time. In general, I don't see the point for that. I would rather cosine
normalize each user row.
I don't know enough yet to comment on what works best, but I can give
some evidence that they do subtract teh row average ahead of time.
Sarwar's previous work, Application of Dimensionality Reduction piece
(http://www.grouplens.org/papers/pdf/webKDD00.pdf) uses the same
prediction function. In section 4.3.1 Prediction Experiment they discuss
the removal of the row average before the SVD computation and it's later
addition for the prediction. I'd make the assumption that the
incremental SVD paper builds on this.
- Richard
