Java Entropy Calculate entropy(int[] histogram)

Description

entropy

License

Apache License

Declaration

public static int entropy(int[] histogram) 

Method Source Code

//package com.java2s;
/*/*from   w  ww . ja v  a  2 s  .  c o  m*/
 * Copyright (C) 2012 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

public class Main {
    public static int entropy(int[] histogram) {
        int total = 0;
        for (int value : histogram) {
            total += value;
        }

        double sum = 0;
        for (int k : histogram) {
            if (k > 0) {
                double p = k * 1.0 / total;
                sum += p * Math.log(p);
            }
        }

        return (int) Math.ceil(-total * sum / Math.log(2));
    }
}

Related

1. entropy(double[] p)
2. entropy(double[] vals)
3. entropy(int hist[])
4. entropy(int numBins, double[] _f)
5. entropy(int total, double[] data)
6. longPseudoEntropy()