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 }