Application: gvSIG desktop

package org.gvsig.raster.lib.buffer.impl.statistics;

import org.gvsig.raster.lib.buffer.api.statistics.StatisticsBand;

/**

 * @author fdiaz

 *

 */

public class VarianceOperation implements StatisticalOperation {

    double sigmaSquare;

    long n;

    double mean;

    double variance;

    /**

     * Variance

     *

     * @param mean

     */

    public VarianceOperation(StatisticsBand statisticsBand) {

        sigmaSquare = 0;

        n = 0;

        this.mean = statisticsBand.getMean();

    }

    @Override

    public void pre() {

        //do nothing

        }

    @Override

    public void addValue(Number value) {

        double doubleValue = value.doubleValue();

        sigmaSquare += Math.pow(doubleValue-this.mean,2);

        n++;

    }

    @Override

    public void post() {

        variance = 0.0;

        if (n > 1L) {

            variance = sigmaSquare/n;

        }

    }

    @Override

    public Object getResult() {

        return variance;

    }

}