g@9646: /** Copyright (C) 2017 by Bundesanstalt für Gewässerkunde
g@9646:  * Software engineering by
g@9646:  *  Björnsen Beratende Ingenieure GmbH
g@9646:  *  Dr. Schumacher Ingenieurbüro für Wasser und Umwelt
g@9646:  *
g@9646:  * This file is Free Software under the GNU AGPL (>=v3)
g@9646:  * and comes with ABSOLUTELY NO WARRANTY! Check out the
g@9646:  * documentation coming with Dive4Elements River for details.
g@9646:  */
g@9646: package org.dive4elements.river.artifacts.model.fixings.fitting;
g@9646: 
g@9646: import java.util.Arrays;
g@9646: 
g@9646: import org.apache.commons.math3.exception.MathIllegalArgumentException;
g@9646: import org.apache.commons.math3.stat.descriptive.AbstractUnivariateStatistic;
g@9646: import org.apache.commons.math3.stat.descriptive.UnivariateStatistic;
g@9646: 
g@9646: /**
g@9646:  * @author Gernot Belger
g@9646:  */
g@9646: final class ChiSquare extends AbstractUnivariateStatistic {
g@9646: 
g@9646:     private final double[] observation;
g@9646: 
g@9646:     public ChiSquare(final double[] observation) {
g@9646:         this.observation = observation;
g@9646:     }
g@9646: 
g@9646:     @Override
g@9646:     public UnivariateStatistic copy() {
g@9646:         /* stateless, hence we can return this */
g@9646:         return this;
g@9646:     }
g@9646: 
g@9646:     @Override
g@9646:     public double evaluate(final double[] values, final int begin, final int length) throws MathIllegalArgumentException {
g@9646:         test(values, begin, length, true);
g@9646: 
g@9646:         final double[] residualsWeights = new double[length];
g@9646:         Arrays.fill(residualsWeights, 0, length - 1, 1.0);
g@9646: 
g@9646:         double cost = 0;
g@9646: 
g@9646:         for (int i = begin; i < begin + length; i++) {
g@9646:             final double residual = values[i + begin] - this.observation[i + begin];
g@9646:             // final double wresiduals = residual * FastMath.sqrt(residualsWeights[i]);
g@9646:             cost += residualsWeights[i] * residual * residual;
g@9646:         }
g@9646: 
g@9646:         return cost;
g@9646:     }
g@9646: }