Ignoring -Inf values in arrays using numpy/scipy in Python

Question

I have an NxM array in numpy that I would like to take the log of, and ignore entries that were negative prior to taking the log. When I take the log of negative entries, it

Answer 1

The easiest way to do this is to use numpy.ma.masked_invalid():

a = numpy.log(numpy.arange(15))
a.sum()
# -inf
numpy.ma.masked_invalid(a).sum()
# 25.19122118273868