/**
* Copyright (C) 2001-2017 by RapidMiner and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapidminer.com
*
* This program is free software: you can redistribute it and/or modify it under the terms of the
* GNU Affero General Public License as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License along with this program.
* If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.validation.clustering.exampledistribution;
/**
* Normalized Gini Coefficient.
*
* @author Michael Wurst
*
*/
public class GiniCoefficient implements ExampleDistributionMeasure {
@Override
public double evaluate(int[] x, int n) {
double sum = 0;
for (int i = 0; i < x.length; i++) {
sum = sum + x[i];
}
double mean = sum / n;
sum = 0;
for (int i = 0; i < x.length; i++) {
for (int j = 0; j < x.length; j++) {
sum = sum + Math.abs(x[i] - x[j]);
}
}
if (mean == 0) {
return 0.0;
}
return 1 - (sum / (2 * mean * (n * ((double) n - 1))));
}
}