# [NumPy-Tickets] [NumPy] #1422: ma._extrema_operation subclasses' reduce method raise ValueError...

NumPy Trac numpy-tickets@scipy....
Sat Mar 6 14:24:35 CST 2010

```#1422: ma._extrema_operation subclasses' reduce method raise ValueError...
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Reporter:  dgoldsmith                              |       Owner:  pierregm
Type:  defect                                  |      Status:  new
Priority:  high                                    |   Milestone:
Component:  numpy.ma                                |     Version:  1.4.0
Keywords:  ma.reduce ValueError "zero-size array"  |
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Comment(by dgoldsmith):

Here's a small self-contained example that reproduces the problem as it
arises from matplotlib's imshow (thanks to Friedrich Romstedt
<friedrichromstedt@gmail.com> for providing it):
{{{
>>> from matplotlib.figure import Figure
>>> argW = numpy.asarray([[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10, 11]])
>>> argW[0:1, 0:0]
array([], shape=(1, 0), dtype=int32)
>>> ax.imshow(argW[0:1, 0:0])
Traceback (most recent call last):
File "<input>", line 1, in <module>
File "C:\Python254\lib\site-packages\matplotlib\axes.py", line 6261, in
imshow
im.autoscale_None()
File "C:\Python254\lib\site-packages\matplotlib\cm.py", line 236, in
autoscale_None
self.norm.autoscale_None(self._A)
File "C:\Python254\lib\site-packages\matplotlib\colors.py", line 792, in
autoscale_None
if self.vmin is None: self.vmin = ma.minimum(A)
File "C:\Python254\Lib\site-packages\numpy\ma\core.py", line 5555, in
__call__
return self.reduce(a)
File "C:\Python254\Lib\site-packages\numpy\ma\core.py", line 5570, in
reduce
t = self.ufunc.reduce(target, **kargs)
ValueError: zero-size array to ufunc.reduce without identity
}}}

--
Ticket URL: <http://projects.scipy.org/numpy/ticket/1422#comment:1>
NumPy <http://projects.scipy.org/numpy>
My example project
```