As you mentioned, you can perform A * b, where A is a rowmatrix and b is a
local matrix.
>From your email, I figure you want to compute b * A^T. To do this, you can
compute C = A b^T, whose result is the transpose of what you were looking
for, i.e. C^T = b * A^T. To undo the transpose, you would have transpose C
manually yourself. Be careful though, because the result might not have
each Row fit in memory on a single machine, which is what RowMatrix
requires. This danger is why we didn't provide a transpose operation in
RowMatrix natively.
To address this and more, there is an effort to provide more comprehensive
linear algebra through block matrices, which will likely make it to 1.3:
https://issues.apache.org/jira/browse/SPARK3434
Best,
Reza
On Mon, Jan 12, 2015 at 6:33 AM, Alex Minnaar <aminnaar@verticalscope.com>
wrote:
> I have a rowMatrix on which I want to perform two multiplications. The
> first is a right multiplication with a local matrix which is fine. But
> after that I also wish to right multiply the transpose of my rowMatrix with
> a different local matrix. I understand that there is no functionality to
> transpose a rowMatrix at this time but I was wondering if anyone could
> suggest a any kind of workaround for this. I had thought that I might be
> able to initially create two rowMatrices  a normal version and a
> transposed version  and use either when appropriate. Can anyone think of
> another alternative?
>
>
> Thanks,
>
>
> Alex
>
