001    /* ===========================================================
002     * JFreeChart : a free chart library for the Java(tm) platform
003     * ===========================================================
004     *
005     * (C) Copyright 2000-2005, 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, 2005, by Object Refinery Limited.
031     *
032     * Original Author:  David Gilbert (for Object Refinery Limited);
033     * Contributor(s):   -;
034     *
035     * $Id: NormalDistributionFunction2D.java,v 1.3.2.2 2005/11/21 10:58:33 mungady Exp $
036     *
037     * Changes
038     * -------
039     * 25-May-2004 : Version 1 (DG);
040     * 21-Nov-2005 : Added getters for the mean and standard deviation (DG);
041     * 
042     */
043    
044    package org.jfree.data.function;
045    
046    /**
047     * A normal distribution function.
048     */
049    public class NormalDistributionFunction2D implements Function2D {
050    
051        /** The mean. */
052        private double mean;
053    
054        /** The standard deviation. */
055        private double std;
056    
057        /**
058         * Constructs a new normal distribution function.
059         *
060         * @param mean  the mean.
061         * @param std  the standard deviation.
062         */
063        public NormalDistributionFunction2D(double mean, double std) {
064            this.mean = mean;
065            this.std = std;
066        }
067        
068        /**
069         * Returns the mean for the function.
070         * 
071         * @return The mean.
072         */
073        public double getMean() {
074            return this.mean;
075        }
076        
077        /**
078         * Returns the standard deviation for the function.
079         * 
080         * @return The standard deviation.
081         */
082        public double getStandardDeviation() {
083            return this.std;
084        }
085    
086        /**
087         * Returns the function value.
088         *
089         * @param x  the x-value.
090         *
091         * @return The value.
092         */
093        public double getValue(double x) {
094            return Math.exp(-1.0 * (x - this.mean) * (x - this.mean) 
095                    / (2 * this.std * this.std)) / Math.sqrt(2 * Math.PI 
096                    * this.std * this.std);
097        }
098    
099    }