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

Bruce Southey bsouthey at gmail.com
Mon Mar 8 09:52:38 EST 2010

On 03/08/2010 01:30 AM, David Goldsmith wrote:
> On Sun, Mar 7, 2010 at 4:41 AM, Friedrich Romstedt 
> <friedrichromstedt at gmail.com <mailto:friedrichromstedt at gmail.com>> wrote:
>     2010/3/5 Pierre GM <pgmdevlist at gmail.com
>     <mailto:pgmdevlist at gmail.com>>:
>     > '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.
>     I would like to stress the fact that imo this is maybe not ticket
>     and not a bug.
>     The issue arises when calling a.max() or similar of empty arrays
>     a, i.e., with:
>     >>> 0 in a.shape
>     True
>     Opposed to the .prod() of an empty array, such a .max() or .min()
>     cannot be defined, because the set is empty.  So it's fully correct to
>     let such calls fail.  Just the failure is a bit deep in numpy, and
>     only the traceback gives some hint what went wrong.
>     I posted something similar also on the matplotlib-users list, sorry
>     for cross-posting thus.
> Any suggestions, then, how to go about figuring out what's happening 
> in my code that's causing this "feature" to manifest itself?
> DG
Perhaps providing the code with specific versions of Python, numpy etc. 
would help.

I would guess that aquarius_test.py has not correctly setup the 
necessary inputs (or has invalid inputs) required by matplotlib (which I 
have no knowledge about). Really you have to find if the _A in cmp.py 
used by 'self.norm.autoscale_None(self._A)' is valid. You may be missing 
a valid initialization step because the TypeError exception in 
autoscale_None ('You must first set_array for mappable') implies 
something need to be done first.


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