[SciPy-user] null space of a matrix - correction
ryanfedora at comcast.net
Wed Jun 29 15:03:47 CDT 2005
Sorry, I meant Robert's submission. I hope that doesn't confuse anyone
trying to follow this thread.
Ryan Krauss wrote:
> This is a completely trivial addition to Robert's submission, but here
> is the function I am using to implement the null function if anyone
> wants to copy and paste it into there own code:
> def null(A, eps=1e-15):
> u, s, vh = scipy.linalg.svd(A)
> null_mask = (s <= eps)
> null_space = scipy.compress(null_mask, vh, axis=0)
> return scipy.transpose(null_space)
> (this assumes you have already got an import scipy somewhere in the file)
> (It made more sense to me to return column vectors.)
> Ryan Krauss wrote:
>> Thanks Robert. This works very well. You seem to always submit high
>> quality input to the list.
>> Robert Kern wrote:
>>> Ryan Krauss wrote:
>>>> This is probably a Numeric question, but is there an easy way to
>>>> find the null space of a matrix in SciPy?
>>> The SVD is one way.
>>> u, s, vh = linalg.svd(A)
>>> null_mask = (s <= eps)
>>> null_space = compress(null_mask, vh, axis=0)
>>> The rows in null_space span the null space of A.
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