What do you mean here? You never need to actually subtract the mean from the data. The similarity metric's math is just adjusted to work as if it were. So no there is no idea of adding back a mean. I don't think there's something not implemented.
On Mon, Nov 26, 2012 at 8:20 PM, Paulo Villegas <[email protected]> wrote: > The thing is, in an Item- or User- based neighborhood recommender, > there's more than one thing that can be centered :-) > > What those papers talk about (from memory, it's been a while since I > last read them, and I don't have them at hand now) is about centering of > the preference around the user's (or item's) average before entering it > in the neighborhood formula. And then moving them back to its usual > range by adding back the average preference (this time for the target > item or user). > > This is something that the code in Mahout does not currently do. You can > check for yourself, the formula is pretty straightforward:
