# File lib/facets/core/enumerable/entropy.rb, line 15 def entropy arr = self.to_a probHash = arr.probability # h is the Shannon entropy of the array h = -1.to_f * probHash.keys.inject(0.to_f) do |sum, i| sum + (probHash[i] * (Math.log(probHash[i])/Math.log(2.to_f))) end h end