[Scipy-tickets] [SciPy] #1318: Degrees of freedom in ndimage.standard_deviation

SciPy Trac scipy-tickets@scipy....
Mon Oct 25 08:55:44 CDT 2010


#1318: Degrees of freedom in ndimage.standard_deviation
---------------------------+------------------------------------------------
 Reporter:  vladan         |       Owner:  somebody
     Type:  enhancement    |      Status:  new     
 Priority:  normal         |   Milestone:  0.9.0   
Component:  scipy.ndimage  |     Version:  0.8.0   
 Keywords:                 |  
---------------------------+------------------------------------------------
 Ndimage.standard_deviation changed its behavior between 0.7 and 0.8. In
 0.7.1:

 In[1]: scipy.ndimage.standard_deviation([1,2,3], [1,1,1], index=1)[[BR]]
 Out[1]: 1.0

 while in 0.8.0:

 In[1]: scipy.ndimage.standard_deviation([1,2,3], [1,1,1], index=1)[[BR]]
 Out[1]: 0.81649658092772626

 It appears that in 0.8 number of degrees of freedom equals N (elements)
 and in 0.7 it was N-1.

 While in my opinion the behavior of 0.8 is correct, perhaps it'd be useful
 to note this change somewhere.

-- 
Ticket URL: <http://projects.scipy.org/scipy/ticket/1318>
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