001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
006 *
007 * Project Info:  http://www.jfree.org/jfreechart/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it 
010 * under the terms of the GNU Lesser General Public License as published by 
011 * the Free Software Foundation; either version 2.1 of the License, or 
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but 
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022 * USA.  
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025 * in the United States and other countries.]
026 *
027 * ---------------------------------
028 * NormalDistributionFunction2D.java
029 * ---------------------------------
030 * (C)opyright 2004-2007, by Object Refinery Limited.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   -;
034 *
035 * Changes
036 * -------
037 * 25-May-2004 : Version 1 (DG);
038 * 21-Nov-2005 : Added getters for the mean and standard deviation (DG);
039 * 
040 */
041
042package org.jfree.data.function;
043
044/**
045 * A normal distribution function.
046 */
047public class NormalDistributionFunction2D implements Function2D {
048
049    /** The mean. */
050    private double mean;
051
052    /** The standard deviation. */
053    private double std;
054
055    /**
056     * Constructs a new normal distribution function.
057     *
058     * @param mean  the mean.
059     * @param std  the standard deviation.
060     */
061    public NormalDistributionFunction2D(double mean, double std) {
062        this.mean = mean;
063        this.std = std;
064    }
065    
066    /**
067     * Returns the mean for the function.
068     * 
069     * @return The mean.
070     */
071    public double getMean() {
072        return this.mean;
073    }
074    
075    /**
076     * Returns the standard deviation for the function.
077     * 
078     * @return The standard deviation.
079     */
080    public double getStandardDeviation() {
081        return this.std;
082    }
083
084    /**
085     * Returns the function value.
086     *
087     * @param x  the x-value.
088     *
089     * @return The value.
090     */
091    public double getValue(double x) {
092        return Math.exp(-1.0 * (x - this.mean) * (x - this.mean) 
093                / (2 * this.std * this.std)) / Math.sqrt(2 * Math.PI 
094                * this.std * this.std);
095    }
096
097}