org.jgap.gp.function.statistics.Variance.java Source code

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Here is the source code for org.jgap.gp.function.statistics.Variance.java

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/*
 * This file is part of JGAP.
 *
 * JGAP offers a dual license model containing the LGPL as well as the MPL.
 *
 * For licensing information please see the file license.txt included with JGAP
 * or have a look at the top of class org.jgap.Chromosome which representatively
 * includes the JGAP license policy applicable for any file delivered with JGAP.
 */
package org.jgap.gp.function.statistics;

import org.apache.commons.math.stat.descriptive.*;
import org.jgap.*;
import org.jgap.gp.*;
import org.jgap.gp.impl.*;
import org.jgap.util.*;

/**
 * Computes the variance of the available values.  The unbiased
 * "sample variance" definitional formula is used:
 * <p>
 * variance = sum((x_i - mean)^2) / (n - 1) </p>
 *
 * @author Luis Garcia
 * @since 3.5
 */
public class Variance extends CommandDynamicArity implements ICloneable {
    public Variance(GPConfiguration a_conf, int a_arityInitial, int a_arityMin, int a_arityMax, Class a_returnType)
            throws InvalidConfigurationException {
        super(a_conf, a_arityInitial, a_arityMin, a_arityMax, a_returnType);
    }

    @Override
    public String toString() {
        String s = "Variance(";
        int size = size();
        for (int i = 0; i < size; i++) {
            if (i > 0) {
                s += ";";
            }
            s += "&" + (i + 1);
        }
        return s + ")";
    }

    @Override
    public double execute_double(ProgramChromosome c, int n, Object[] args) {
        int size = size();
        DescriptiveStatistics stats = new DescriptiveStatistics();
        for (int i = 0; i < size; i++) {
            stats.addValue(c.execute_double(n, i, args));
        }
        return stats.getVariance();
    }

    @Override
    public float execute_float(ProgramChromosome c, int n, Object[] args) {
        int size = size();
        DescriptiveStatistics stats = new DescriptiveStatistics();
        for (int i = 0; i < size; i++) {
            stats.addValue(c.execute_float(n, i, args));
        }
        return (float) stats.getVariance();
    }

    public Object clone() {
        try {
            Variance result = new Variance(getGPConfiguration(), getArity(null), getArityMin(), getArityMax(),
                    getReturnType());
            return result;
        } catch (Exception ex) {
            throw new CloneException(ex);
        }
    }

    @Override
    public String getName() {
        return "Variance";
    }
}