01: /*
02: * (c) Copyright 2006 by Volker Bergmann. All rights reserved.
03: *
04: * Redistribution and use in source and binary forms, with or without
05: * modification, is permitted under the terms of the
06: * GNU General Public License.
07: *
08: * For redistributing this software or a derivative work under a license other
09: * than the GPL-compatible Free Software License as defined by the Free
10: * Software Foundation or approved by OSI, you must first obtain a commercial
11: * license to this software product from Volker Bergmann.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
14: * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
15: * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
16: * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
17: * HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
18: * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
19: * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
20: * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
21: * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
22: * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
23: * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
24: * POSSIBILITY OF SUCH DAMAGE.
25: */
26:
27: package org.databene.benerator.primitive.number.distribution;
28:
29: import org.databene.benerator.WeightFunction;
30:
31: /**
32: * Gaussian Function. 1/(deviation*sqrt(2PI)) * e^(-(x - average)^2/(4 * deviation^2)).<br/>
33: * <br/>
34: * Created: 10.06.2006 05:37:56
35: */
36: public class GaussianFunction implements WeightFunction {
37:
38: /** the average value */
39: private double average;
40:
41: /** the deviation */
42: private double deviation;
43:
44: /** a constant scale factor of the function */
45: private double scale;
46:
47: // constructors ----------------------------------------------------------------------------------------------------
48:
49: /** Fully Initializes the faunction */
50: public GaussianFunction(double average, double deviation) {
51: this .average = average;
52: this .deviation = deviation;
53: this .scale = 1. / deviation / Math.sqrt(2 * Math.PI);
54: }
55:
56: // properties ------------------------------------------------------------------------------------------------------
57:
58: /** returns the average */
59: public double getAverage() {
60: return average;
61: }
62:
63: /** returns the deviation */
64: public double getDeviation() {
65: return deviation;
66: }
67:
68: // WeightFunction implementation -----------------------------------------------------------------------------------------
69:
70: /** calculates the value */
71: public double value(double param) {
72: double x = (param - average) / deviation;
73: return scale * Math.exp(-0.5 * x * x);
74: }
75:
76: /** Creates a Stirng representation of the function */
77: public String toString() {
78: return getClass().getSimpleName() + "[1. / (" + deviation
79: + "*sqrt(2*PI)) * e^(-"
80: + (average != 0 ? "(x - " + average + ")" : "x")
81: + "^2/" + (2 * deviation * deviation) + ")]";
82: }
83: }
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