[Numpy-discussion] Is this a bug in numpy.ma.reduce?

David Goldsmith d.l.goldsmith at gmail.com
Fri Mar 5 12:43:46 EST 2010

On Fri, Mar 5, 2010 at 9:22 AM, David Goldsmith <d.l.goldsmith at gmail.com>wrote:

> On Fri, Mar 5, 2010 at 2:51 AM, Pierre GM <pgmdevlist at gmail.com> wrote:
>> On Mar 5, 2010, at 4:38 AM, David Goldsmith wrote:
>> > Hi!  Sorry for the cross-post, but my own investigation has led me to
>> suspect that mine is actually a numpy problem, not a matplotlib problem.
>>  I'm getting the following traceback from a call to matplotlib.imshow:
>> > ...
>> > Based on examination of the code, the last self is an instance of
>> ma._extrema_operation (or one of its subclasses) - is there a reason why
>> this class is unable to deal with a "zero-size array to ufunc.reduce without
>> identity," (i.e., was it thought that it would - or should - never get one)
>> or was this merely an oversight?  Either way, there's other instances on the
>> lists of this error cropping up, so this circumstance should probably be
>> handled more robustly.  In the meantime, workaround?
>> 'm'fraid no. I gonna have to investigate that. Please open a ticket with a
>> self-contained example that reproduces the issue.
> I'll do my best, but since it's a call from matplotlib and I don't really
> know what's causing the problem (other than a literal reading of the
> exception) I'm not sure I can.

Well, that was easy:

mn = N.ma.core._minimum_operation()
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:\Python254\Lib\site-packages\numpy\ma\core.py", line 5570, in
    t = self.ufunc.reduce(target, **kargs)
ValueError: zero-size array to ufunc.reduce without identity

I'll file a ticket.


> DG
>> Thx in advance...
>> P.
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