Source for org.jfree.data.function.NormalDistributionFunction2D

   1: /* ===========================================================
   2:  * JFreeChart : a free chart library for the Java(tm) platform
   3:  * ===========================================================
   4:  *
   5:  * (C) Copyright 2000-2007, 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
  20:  * License along with this library; if not, write to the Free Software
  21:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
  22:  * USA.  
  23:  *
  24:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
  25:  * in the United States and other countries.]
  26:  *
  27:  * ---------------------------------
  28:  * NormalDistributionFunction2D.java
  29:  * ---------------------------------
  30:  * (C)opyright 2004-2007, by Object Refinery Limited.
  31:  *
  32:  * Original Author:  David Gilbert (for Object Refinery Limited);
  33:  * Contributor(s):   -;
  34:  *
  35:  * Changes
  36:  * -------
  37:  * 25-May-2004 : Version 1 (DG);
  38:  * 21-Nov-2005 : Added getters for the mean and standard deviation (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 mean for the function.
  68:      * 
  69:      * @return The mean.
  70:      */
  71:     public double getMean() {
  72:         return this.mean;
  73:     }
  74:     
  75:     /**
  76:      * Returns the standard deviation for the function.
  77:      * 
  78:      * @return The standard deviation.
  79:      */
  80:     public double getStandardDeviation() {
  81:         return this.std;
  82:     }
  83: 
  84:     /**
  85:      * Returns the function value.
  86:      *
  87:      * @param x  the x-value.
  88:      *
  89:      * @return The value.
  90:      */
  91:     public double getValue(double x) {
  92:         return Math.exp(-1.0 * (x - this.mean) * (x - this.mean) 
  93:                 / (2 * this.std * this.std)) / Math.sqrt(2 * Math.PI 
  94:                 * this.std * this.std);
  95:     }
  96: 
  97: }