numpy: Efficiently avoid 0s when taking log(matrix)

Question

from numpy import *

m = array([[1,0],
           [2,3]])

I would like to compute the element-wise log2(m), but only in the places whe

Answer 1

We can use masked arrays for this:

>>> from numpy import *
>>> m = array([[1,0], [2,3]])
>>> x = ma.log(m)
>>> print x.filled(0)
[[ 0.          0.        ]
 [ 0.69314718  1.09861229]]