[Numpy-discussion] unexpected behaviour of numpy.var

Travis Oliphant oliphant at ee.byu.edu
Tue Aug 1 14:54:46 CDT 2006


Sasha wrote:

>I cannot reproduce your results, but I wonder if the following is right:
>
>  
>
>>>>a = array([1,2,3,4,5])
>>>>var(a[newaxis,:])
>>>>        
>>>>
>array([ 0.,  0.,  0.,  0.,  0.])
>  
>
>>>>a[newaxis,:].var()
>>>>        
>>>>
>2.0
>  
>
>>>>a[newaxis,:].var(axis=0)
>>>>        
>>>>
>array([ 0.,  0.,  0.,  0.,  0.])
>
>Are method and function supposed to have different defaults?  It looks
>like the method defaults to variance over all axes while the function
>defaults to axis=0.
>
>  
>
They are supposed to have different defaults because the functional 
forms are largely for backward compatibility where axis=0 was the default. 

-Travis





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