[SciPy-user] bug in scipy array?

Robert Kern robert.kern at gmail.com
Tue Mar 28 15:01:16 CST 2006


Kilian Koepsell wrote:
> hi,
> 
> i came across the following strange behavior while multiplying a  
> scipy array:
> a[:,2:] gives a column of zeros if a is an 2x2 array (that is correct)
> but if i multiply this column by zero, it affects the element a[2,0]  
> which is probably a bug.
> 
>   >>> from scipy import *
>   >>> a = array([[1,2],[3,4]])
>   >>> a
>   array([[1, 2],
>          [3, 4]])
>   >>> a[:,2:]
>   zeros((2, 0), 'l')
>   >>> a[:,2:] *= 0
>   >>> a
>   array([[1, 2],
>          [0, 4]])
> 
> i am using scipy 0.3.2 with python 2.4.2 and Mac OSX 10.4.5.

This is a bug in Numeric 24.x. This bug does not appear in current versions of
numpy, Numeric's replacement.

In [37]: import numpy

In [38]: import Numeric

In [39]: a = numpy.array([[1, 2], [3, 4]])

In [40]: a[:,2:] *= 0

In [41]: a
Out[41]:
array([[1, 2],
       [3, 4]])

In [42]: a = Numeric.array([[1, 2], [3, 4]])

In [43]: a[:,2:] *= 0

In [44]: a
Out[44]:
array([[0, 2],
       [0, 4]])

-- 
Robert Kern
robert.kern at gmail.com

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco



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