001 /* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2007, 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 2004-2007, by Object Refinery Limited.
031 *
032 * Original Author: David Gilbert (for Object Refinery Limited);
033 * Contributor(s): -;
034 *
035 * Changes
036 * -------
037 * 25-May-2004 : Version 1 (DG);
038 * 21-Nov-2005 : Added getters for the mean and standard deviation (DG);
039 *
040 */
041
042 package org.jfree.data.function;
043
044 /**
045 * A normal distribution function.
046 */
047 public class NormalDistributionFunction2D implements Function2D {
048
049 /** The mean. */
050 private double mean;
051
052 /** The standard deviation. */
053 private double std;
054
055 /**
056 * Constructs a new normal distribution function.
057 *
058 * @param mean the mean.
059 * @param std the standard deviation.
060 */
061 public NormalDistributionFunction2D(double mean, double std) {
062 this.mean = mean;
063 this.std = std;
064 }
065
066 /**
067 * Returns the mean for the function.
068 *
069 * @return The mean.
070 */
071 public double getMean() {
072 return this.mean;
073 }
074
075 /**
076 * Returns the standard deviation for the function.
077 *
078 * @return The standard deviation.
079 */
080 public double getStandardDeviation() {
081 return this.std;
082 }
083
084 /**
085 * Returns the function value.
086 *
087 * @param x the x-value.
088 *
089 * @return The value.
090 */
091 public double getValue(double x) {
092 return Math.exp(-1.0 * (x - this.mean) * (x - this.mean)
093 / (2 * this.std * this.std)) / Math.sqrt(2 * Math.PI
094 * this.std * this.std);
095 }
096
097 }