ok column-wise mean. (the mean of all rows).
On Mon, Dec 5, 2011 at 11:00 AM, Ted Dunning <[email protected]> wrote: > 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! >> > > > >> > > > >> > > >> > >>
