[eigen] Computing left nullspace of A when rows > cols

[W. James MacLean <james.maclean@xxxxxxxxxxx>]

Hi,

I would like to use Eigen to compute the left nullspace of a matrix A where
A is n by m, and n > m. Assuming we denote the decomposition as A = U S
V^*, then (currently) the U returned by Eigen is n by m, and the columns
corresponding to the left nullspace are missing.

Is it possible to either (1) compute these easily using some other facility
already in Eigen, or (2) modify Eigen so it outputs the full n by n U
matrix?

I know that, generally, I could do this by transposing A and computing the
right nullspace, but then cols > rows and Eigen doesn't seem to support
this for SVD at present.

Cheers,

James

PS- I *really really* like what I've seen of Eigen so far - way cool!