I am using numpy.log10 to calculate the log of an array of probability values. There are some zeros in the array, and I am trying to get around it using
result = numpy.where(prob > 0.0000000001, numpy.log10(prob), -10)
However, RuntimeWarning: divide by zero encountered in log10
still appeared and I am sure it is this line caused the warning.
Although my problem is solved, I am confused why this warning appeared again and again?
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Answer
numpy.log10(prob)
calculates the base 10 logarithm for all elements of prob
, even the ones that aren’t selected by the where
. If you want, you can fill the zeros of prob
with 10**-10
or some dummy value before taking the logarithm to get rid of the problem. (Make sure you don’t compute prob > 0.0000000001
with dummy values, though.)