How do I compute the approximate entropy of a bit string?

Question

Is there a standard way to do this?

Googling -- \"approximate entropy\" bits -- uncovers multiple academic papers but I\'d like to just find a chunk of pseudocode de

Answer 1

Using Shannon entropy of a word with this formula : http://imgur.com/a/DpcIH

Here's a O(n) algorithm that calculates it :

import math
from collections import Counter


def entropy(s):
    l = float(len(s))
    return -sum(map(lambda a: (a/l)*math.log2(a/l), Counter(s).values()))