playground.johannes.socialnetworks.statistics.LogNormalDistribution.java Source code

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Here is the source code for playground.johannes.socialnetworks.statistics.LogNormalDistribution.java

Source

/* *********************************************************************** *
 * project: org.matsim.*
 * LogNormalDistribution.java
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 * copyright       : (C) 2011 by the members listed in the COPYING,        *
 *                   LICENSE and WARRANTY file.                            *
 * email           : info at matsim dot org                                *
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *   See also COPYING, LICENSE and WARRANTY file                           *
 *                                                                         *
 * *********************************************************************** */
package playground.johannes.socialnetworks.statistics;

import org.apache.commons.math.FunctionEvaluationException;
import org.apache.commons.math.analysis.UnivariateRealFunction;

/**
 * @author illenberger
 *
 */
public class LogNormalDistribution implements UnivariateRealFunction {

    private final double sigma;

    private final double mu;

    private final double intercept;

    public LogNormalDistribution(double sigma, double mu, double intercept) {
        this.sigma = sigma;
        this.mu = mu;
        this.intercept = intercept;
    }

    @Override
    public double value(double x) throws FunctionEvaluationException {
        return intercept / (Math.sqrt(2 * Math.PI) * sigma * x)
                * Math.exp(-Math.pow(Math.log(x) - mu, 2) / (2 * Math.pow(sigma, 2)));
    }

}