Row-wise mean usually means that a mean of each row is computed. I think that most PCA users would want column-wise means for subtraction.
On Mon, Dec 5, 2011 at 10:58 AM, Dmitriy Lyubimov <[email protected]> wrote: > We probably need row wise mean computation job anyway as a separate mr > step. Wanna take a stab? > On Dec 5, 2011 10:34 AM, "Raphael Cendrillon" <[email protected]> > wrote: > > > Given that this request seems to come up frequently, would it be worth > > putting this approach under mahout-examples? Initially it could use the > > brute force approach together with SSVD, and updated later once support > is > > ready for mean-subtraction within SSVD. > > > > I could put something together if there's interest. > > > > On Mon, Dec 5, 2011 at 9:40 AM, Dmitriy Lyubimov <[email protected]> > > wrote: > > > > > I am working on the addtions to ssvd algorithms and the mods to current > > > solver will probably emerge in a matter of a month, my schedule > > permitting. > > > > > > However, a brute force approach is already possible. If your input is > of > > > moderate size, or if it is already dense, you could compute median and > > > substract it yourself very easily and then shove it into ssvd solver > > while > > > requesting to produce either u or v depending if subtract column wise > or > > > row wise mean. > > > > > > The only problem with brute force approach is that it would densify > > > originally sparse input. Depending on your problem and # of machine > nodes > > > you can spare, it may or may not be a problem. > > > On Dec 4, 2011 7:59 PM, "magicalo" <[email protected]> wrote: > > > > > > > Hello, > > > > > > > > Is there an expected release date for the PCA algorithm as part of > > > Mahout? > > > > Tx! > > > > > > > > > > > > > >
