harmonic mean in python

Question

The Harmonic Mean function in Python (scipy.stats.hmean) requires that the input be positive numbers.

For example:

from scipy import st         


        

Answer 1

The harmonic mean is only defined for sets of positive real numbers. If you try and compute it for sets with negatives you get all kinds of strange and useless results even if you don't hit div by 0. For example, applying the formula to the set (3, -3, 4) gives a mean of 12!