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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: }