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 }