01: /* ===========================================================
02: * JFreeChart : a free chart library for the Java(tm) platform
03: * ===========================================================
04: *
05: * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
06: *
07: * Project Info: http://www.jfree.org/jfreechart/index.html
08: *
09: * 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, 2005, by Object Refinery Limited.
31: *
32: * Original Author: David Gilbert (for Object Refinery Limited);
33: * Contributor(s): -;
34: *
35: * $Id: NormalDistributionFunction2D.java,v 1.3.2.2 2005/11/21 10:58:33 mungady Exp $
36: *
37: * Changes
38: * -------
39: * 25-May-2004 : Version 1 (DG);
40: * 21-Nov-2005 : Added getters for the mean and standard deviation (DG);
41: *
42: */
43:
44: package org.jfree.data.function;
45:
46: /**
47: * A normal distribution function.
48: */
49: public class NormalDistributionFunction2D implements Function2D {
50:
51: /** The mean. */
52: private double mean;
53:
54: /** The standard deviation. */
55: private double std;
56:
57: /**
58: * Constructs a new normal distribution function.
59: *
60: * @param mean the mean.
61: * @param std the standard deviation.
62: */
63: public NormalDistributionFunction2D(double mean, double std) {
64: this .mean = mean;
65: this .std = std;
66: }
67:
68: /**
69: * Returns the mean for the function.
70: *
71: * @return The mean.
72: */
73: public double getMean() {
74: return this .mean;
75: }
76:
77: /**
78: * Returns the standard deviation for the function.
79: *
80: * @return The standard deviation.
81: */
82: public double getStandardDeviation() {
83: return this .std;
84: }
85:
86: /**
87: * Returns the function value.
88: *
89: * @param x the x-value.
90: *
91: * @return The value.
92: */
93: public double getValue(double x) {
94: return Math.exp(-1.0 * (x - this .mean) * (x - this .mean)
95: / (2 * this .std * this .std))
96: / Math.sqrt(2 * Math.PI * this.std * this.std);
97: }
98:
99: }
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