On Wed, Oct 31, 2012 at 8:21 AM, Perko, Ralph J <Ralph.Perko@pnnl.gov> wrote:
> I am using the mahout pca function to project a set of documents into 2d space. From
what I understand, the pca function in mahout generates a [U] matrix using a
Yes, more specifically, you probably need U*Sigma output (us true option)
[V] matrix for translation from the highdimensional data
representation to the 2d representation. Is there a way that I can
specify the [V] matrix if I already have one I would like for it to
use?
if you already have V, you don't need to run SVD. You need a result of
multiplication (AM)V which is very closely same as U*Sigma output.
This is something else than what SSVD does. "SSVD pca true" finds
SVD of AM (or AXi in the docs) which is a more complicated task than
just (AM)V
You can compute (AM) V with help of DistributedMatrix matrix
operations. There's column mean computation and matrix multiplication.
(not immediately sure if multiplication with vector subtraction can be
combined in one run).
>
> Thanks,
> Ralph
> __________________________________________________
> Ralph Perko
> Pacific Northwest National Laboratory
>
>
