[Numpy-discussion] matrix.std() returns array
Keith Goodman
kwgoodman at gmail.com
Wed Apr 26 21:46:08 CDT 2006
I noticed that the mean of a matrix is a matrix but the standard
deviation of a matrix is an array. Is that the expected behavior? I'm
also getting the wrong values (0 and nan) for the standard deviation.
Did I mess something up?
I'm trying to learn scipy (and python) by porting a small Octave
program. I installed numpy from svn (today) on a Debian box. And
numpy.test() says OK.
Here's an example:
>> numpy.__version__
'0.9.7.2416'
>> x = asmatrix(random.uniform(0,1,(3,3)))
>> x
matrix([[ 0.56771284, 0.57053769, 0.57505946],
[ 0.10479534, 0.81692248, 0.91829316],
[ 0.48627829, 0.59255983, 0.32628573]])
>> x.mean(0)
matrix([[ 0.38626216, 0.66000667, 0.60654612]])
>> x.std(0)
array([ nan, 0. , 0. ])
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