1. /* ===========================================================

  2.  * JFreeChart : a free chart library for the Java(tm) platform

  3.  * ===========================================================

  4.  *

  5.  * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.

  6.  *

  7.  * Project Info:  http://www.jfree.org/jfreechart/index.html

  8.  *

  9.  * This library is free software; you can redistribute it and/or modify it 

  10.  * under the terms of the GNU Lesser General Public License as published by 

  11.  * the Free Software Foundation; either version 2.1 of the License, or 

  12.  * (at your option) any later version.

  13.  *

  14.  * This library is distributed in the hope that it will be useful, but 

  15.  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 

  16.  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 

  17.  * License for more details.

  18.  *

  19.  * You should have received a copy of the GNU Lesser General Public License 

  20.  * along with this library; if not, write to the Free Software Foundation, 

  21.  * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.

  22.  *

  23.  * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 

  24.  * in the United States and other countries.]

  25.  *

  26.  * ---------------------------------

  27.  * NormalDistributionFunction2D.java

  28.  * ---------------------------------

  29.  * (C)opyright 2004, by Object Refinery Limited.

  30.  *

  31.  * Original Author:  David Gilbert (for Object Refinery Limited);

  32.  * Contributor(s):   -;

  33.  *

  34.  * $Id: NormalDistributionFunction2D.java,v 1.3 2005/02/24 10:44:45 mungady Exp $

  35.  *

  36.  * Changes

  37.  * -------

  38.  * 25-May-2004 : Version 1(DG);

  39.  * 

  40.  */

  41. 

  42. package org.jfree.data.function;

  43. 

  44. /**

  45.  * A normal distribution function.

  46.  */

  47. public class NormalDistributionFunction2D implements Function2D {

  48. 

  49.     /** The mean. */

  50.     private double mean;

  51. 

  52.     /** The standard deviation. */

  53.     private double std;

  54. 

  55.     /**

  56.      * Constructs a new normal distribution function.

  57.      *

  58.      * @param mean  the mean.

  59.      * @param std  the standard deviation.

  60.      */

  61.     public NormalDistributionFunction2D(double mean, double std) {

  62.         this.mean = mean;

  63.         this.std = std;

  64.     }

  65. 

  66.     /**

  67.      * Returns the function value.

  68.      *

  69.      * @param x  the x-value.

  70.      *

  71.      * @return The value.

  72.      */

  73.     public double getValue(double x) {

  74.         return Math.exp(

  75.             -1.0 

  76.             * (x - this.mean) * (x - this.mean) / (2 * this.std * this.std))

  77.             / Math.sqrt(2 * Math.PI * this.std * this.std

  78.         );

  79.     }

  80. 

  81. }