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

Vincent Schut schut at sarvision.nl
Fri Mar 5 06:04:32 EST 2010

On 03/05/2010 11:51 AM, Pierre GM 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.
> Thx in advance...
> P.

This might be completely wrong, but I seem to remember a similar issue, 
which I then traced down to having a masked array with a mask that was 
set to True or False, instead of being a full fledged bool mask array. I 
was in a hurry then and completely forgot about it later, so filed no 
bug report whatsoever, for which I apologize.


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