org.peerfact.impl.util.stats.distributions.PoissonDistribution.java Source code

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Here is the source code for org.peerfact.impl.util.stats.distributions.PoissonDistribution.java

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/*
 * Copyright (c) 2012-2013 Open Source Community - <http://www.peerfact.org>
 * Copyright (c) 2011-2012 University of Paderborn - UPB
 * Copyright (c) 2005-2011 KOM - Multimedia Communications Lab
 *
 * This file is part of PeerfactSim.KOM.
 * 
 * PeerfactSim.KOM is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version.
 * 
 * PeerfactSim.KOM 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with PeerfactSim.KOM.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package org.peerfact.impl.util.stats.distributions;

import org.apache.commons.math.MathException;
import org.apache.commons.math.distribution.PoissonDistributionImpl;
import org.peerfact.impl.scenario.XMLConfigurableConstructor;
import org.peerfact.impl.simengine.Simulator;

/**
 * 
 * @author <info@peerfact.org>
 * @version 05/06/2011
 * 
 */
public class PoissonDistribution implements Distribution {
    private double lambda;

    private PoissonDistributionImpl poisson;

    @XMLConfigurableConstructor({ "lambda" })
    public PoissonDistribution(double lambda) {
        this.lambda = lambda;
        this.poisson = new PoissonDistributionImpl(lambda);
    }

    // returns the x-value for a random value in the cdf
    @Override
    public double returnValue() {
        double random = Simulator.getRandom().nextDouble();
        int result;

        try {
            result = poisson.inverseCumulativeProbability(random);
        } catch (MathException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            result = 0;
        }

        return result;
    }

    /**
     * returns a random value Poisson distributed with lamda = _lamda.
     * 
     * @param _lamda
     * @return as double
     */
    public static double returnValue(double _lamda) {
        try {
            PoissonDistributionImpl d = new PoissonDistributionImpl(_lamda);
            return d.inverseCumulativeProbability(Simulator.getRandom().nextDouble());
        } catch (MathException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return 0;
        }
    }

    @Override
    public String toString() {
        return "PoissonDistribution [lambda=" + lambda + "]";
    }

    @Override
    public void writeBackToXML(BackWriter bw) {
        bw.writeSimpleType("lambda", lambda);
    }

}