[Numpy-discussion] What's wrong with matrices?
JJ
josh8912 at yahoo.com
Sun Jul 9 03:23:54 CDT 2006
Ed Schofield <schofield <at> ftw.at> writes:
>
>
> On 08/07/2006, at 10:22 PM, JJ wrote:
>
> > 3) In some operations, especially range selection operations, a N,
> > 1 matrix is
> > turned into a 1,N matrix. This is confusing relative to matlab and
> > problematic,
> > in my view.
>
> This sounds like a bug. Can you give any examples of this happening
> with the latest release or SVN version?
>
> > <snip>
> >
> > 5) If X is a 1,n matrix, then X.T should return a n,1 matrix, I
> > think.
>
> This should be the case. Could you post a code snippet that violates
> it?
>
> Thanks for your feedback, JJ!
>--------------------------------------------------
Hi Ed:
Here are a couple more items:
c = cov(a) # a is a matrix
type(c) # should be a matrix
<type 'numpy.ndarray'>
Also, if a is 5x2, then cov(a) is 5,5. Is that just a convention? I would
expect the cov to be 2,2, as in matlab. It means I have to use more transpose
methods.
D is a 1,n matrix
(D<2).nonzero()[0]
As per my earlier comment on which(), I wish that .nonzero() did not return a
tupple.
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