[Numpy-discussion] Bug? numpy.matrix.sum()

Alan G Isaac aisaac at american.edu
Fri Jan 20 07:03:03 CST 2006


On Fri, 20 Jan 2006, Norbert Nemec apparently wrote: 
> In [1]: import numpy 

> In [2]: numpy.__version__ 
> Out[2]: '0.9.2' 

> In [3]: a = numpy.matrix(numpy.eye(2)) 

> In [4]: a.sum() 
> Out[4]: matrix([[1, 0, 0, 1]]) 

> In [5]: a.A.sum() 
> Out[5]: 2 

> In [6]: sum(a) 
> Out[6]: matrix([[1, 1]]) 

> In [7]: sum(a.A) 
> Out[7]: array([1, 1]) 


Only [4] looks wrong.
However it works "right" if you provide a numerical axis 
argument.  (I put "right" in quotes because it is not clear 
to me that a row vector is expected as the result when 
summing columns.) The default is axis=None, which is not 
working as expected for matrices.

Cheers,
Alan Isaac







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