[Numpy-discussion] Why NaN?

Gökhan Sever gokhansever@gmail....
Tue Aug 4 11:46:57 CDT 2009


Hello,

I know this has to have a very simple answer, but stuck at this very moment
and can't get a meaningful result out of np.mean()


In [121]: a = array([NaN, 4, NaN, 12])

In [122]: b = array([NaN, 2, NaN, 3])

In [123]: c = a/b

In [124]: mean(c)
Out[124]: nan

In [125]: mean a
--------> mean(a)
Out[125]: nan

Further when I tried:

In [138]: c
Out[138]: array([ NaN,   2.,  NaN,   4.])

In [139]: np.where(c==NaN)
Out[139]: (array([], dtype=int32),)


In [141]: mask = [c != NaN]

In [142]: mask
Out[142]: [array([ True,  True,  True,  True], dtype=bool)]


Any ideas?

-- 
Gökhan
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