[Numpy-discussion] not expected output of fill_diagonal

[Warren Weckesser]

On Fri, Jun 8, 2012 at 7:45 PM, Frédéric Bastien <nouiz at nouiz.org> wrote:

> Hi,
>
> While reviewing the Theano op that wrap numpy.fill_diagonal, we found
> an unexpected behavior of it:
>
> # as expected for square matrix
> >>> a=numpy.zeros((5,5))
> >>> numpy.fill_diagonal(a, 10)
> >>> print a
>
> # as expected long rectangular matrix
> >>> a=numpy.zeros((3,5))
> >>> numpy.fill_diagonal(a, 10)
> >>> print a
> [[ 10.   0.   0.   0.   0.]
>  [  0.  10.   0.   0.   0.]
>  [  0.   0.  10.   0.   0.]]
>
> # Not as expected
> >>> a=numpy.zeros((5,3))
> >>> numpy.fill_diagonal(a, 10)
> >>> print a
> [[ 10.   0.   0.]
>  [  0.  10.   0.]
>  [  0.   0.  10.]
>  [  0.   0.   0.]
>  [ 10.   0.   0.]]
>
>
> I can make a PR that will add a parameter wrap that allow to control
> if it return the old behavior or what I would expect in the last case:
> [[ 10.   0.   0.]
>  [  0.  10.   0.]
>  [  0.   0.  10.]
>  [  0.   0.   0.]
>  [  0.   0.   0.]]
>
> My questions is, do someone else expect the current behavior? Should
> we change the default to be what I expect? Do you want that we warn if
> the user didn't specify witch behavior and in the future we change it?
>
>

There is a ticket for this:

    http://projects.scipy.org/numpy/ticket/1953

I agree that the behavior is unexpected and should be fixed.

Warren



> Anything else I didn't think?
>
> thanks
>
> Fred
> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion at scipy.org
> http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/numpy-discussion/attachments/20120609/8f974e84/attachment.html>