yuanmai · December 14, 2015 04:19
diff --git a/entropy.clj b/entropy.clj
 (defn shannon-entropy [col]    
  (let [xs  (vals (frequencies col))
        n   (apply + xs)
        ln2 (Math/log 2)]
    (-
     (apply +
            (for [x xs]
              (let [a (/ x n)]
                (* a (/ (Math/log a) ln2))))))))
diff --git a/repl.clj b/repl.clj
 user> (shannon-entropy [1 2 3 4 5 6 7 8])
 3.0
 user> (shannon-entropy [1 2 3 4 5 6 7])
 2.8073549220576046
 user> (shannon-entropy [1 2 3 4 5 6 7 6 5 4 3 2 1])
 2.7773627950641684
 user> (shannon-entropy [1 2 3 4 5 6 7 6 5 4 3 2 1 99])
 2.950212064914748