[SciPy-User] zscore axis functionality is borked

Alacast alacast@gmail....
Wed Nov 30 14:25:43 CST 2011


axis=0 (the default) works fine. axis=1, etc, is clearly wrong. Am I
misunderstanding how to use this, or is this a bug?

In [16]: i = rand(4,4)

In [17]: i
Out[17]:
array([[ 0.85367762,  0.25348857,  0.23572615,  0.50403358],
       [ 0.70199066,  0.81872151,  0.47357357,  0.20425537],
       [ 0.31042673,  0.25837984,  0.73550134,  0.57970176],
       [ 0.42828877,  0.60988596,  0.04059321,  0.73944219]])

In [18]: zscore(i, axis=0)
Out[18]:
array([[ 1.30128758, -0.96195723, -0.52119142, -0.01453907],
       [ 0.59653471,  1.38544585,  0.39284654, -1.55756529],
       [-1.22271057, -0.94164388,  1.39942427,  0.37494213],
       [-0.67511172,  0.51815526, -1.27107939,  1.19716222]])

In [19]: zscore(i[:,0])
Out[19]: array([ 1.30128758,  0.59653471, -1.22271057, -0.67511172])

In [20]: zscore(i[:,0])==zscore(i,axis=0)[:,0]
Out[20]: array([ True,  True,  True,  True], dtype=bool)

In [21]: zscore(i, axis=1)
Out[21]:
array([[-0.99378502, -1.59397407, -1.61173649, -1.34342906],
       [-1.6379836 , -1.52125275, -1.86640069, -2.13571889],
       [-2.09968257, -2.15172946, -1.67460796, -1.83040754],
       [-1.29796925, -1.11637205, -1.68566481, -0.98681582]])
#The above is obviously wrong, as everything has a negative z score

In [22]: zscore(i[0,:])
Out[22]: array([ 1.56824016, -0.83321371, -0.90428403,  0.16925757])

In [23]: zscore(i[0,:])==zscore(i,axis=1)[0,:]
Out[23]: array([False, False, False, False], dtype=bool)
#Using axis=1 produces different results from taking a row directly.

In [24]: zscore(i, axis=-1)
Out[24]:
array([[-0.99378502, -1.59397407, -1.61173649, -1.34342906],
       [-1.6379836 , -1.52125275, -1.86640069, -2.13571889],
       [-2.09968257, -2.15172946, -1.67460796, -1.83040754],
       [-1.29796925, -1.11637205, -1.68566481, -0.98681582]])
#Getting rows by using axis=-1 is no better (this is the same result as
axis=1
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