KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > apache > commons > math > distribution > GammaDistributionTest


1 /*
2  * Copyright 2003-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.math.distribution;
18
19 /**
20  * Test cases for GammaDistribution.
21  * Extends ContinuousDistributionAbstractTest. See class javadoc for
22  * ContinuousDistributionAbstractTest for details.
23  *
24  * @version $Revision$ $Date: 2005-06-26 15:25:41 -0700 (Sun, 26 Jun 2005) $
25  */
26 public class GammaDistributionTest extends ContinuousDistributionAbstractTest {
27     
28     /**
29      * Constructor for GammaDistributionTest.
30      * @param name
31      */
32     public GammaDistributionTest(String JavaDoc name) {
33         super(name);
34     }
35     
36     //-------------- Implementations for abstract methods -----------------------
37
38     /** Creates the default continuous distribution instance to use in tests. */
39     public ContinuousDistribution makeDistribution() {
40         return DistributionFactory.newInstance().createGammaDistribution(4d, 2d);
41     }
42     
43     /** Creates the default cumulative probability distribution test input values */
44     public double[] makeCumulativeTestPoints() {
45         // quantiles computed using R version 1.8.1 (linux version)
46 return new double[] {0.8571048, 1.646497, 2.179731, 2.732637,
47             3.489539, 26.12448, 20.09024, 17.53455,
48             15.50731, 13.36157};
49     }
50     
51     /** Creates the default cumulative probability density test expected values */
52     public double[] makeCumulativeTestValues() {
53         return new double[] {0.001d, 0.01d, 0.025d, 0.05d, 0.1d, 0.999d,
54                 0.990d, 0.975d, 0.950d, 0.900d};
55     }
56     
57     // --------------------- Override tolerance --------------
58 protected void setup() throws Exception JavaDoc {
59         super.setUp();
60         setTolerance(1E-6);
61     }
62
63     //---------------------------- Additional test cases -------------------------
64 public void testParameterAccessors() {
65         GammaDistribution distribution = (GammaDistribution) getDistribution();
66         assertEquals(4d, distribution.getAlpha(), 0);
67         distribution.setAlpha(3d);
68         assertEquals(3d, distribution.getAlpha(), 0);
69         assertEquals(2d, distribution.getBeta(), 0);
70         distribution.setBeta(4d);
71         assertEquals(4d, distribution.getBeta(), 0);
72         try {
73             distribution.setAlpha(0d);
74             fail("Expecting IllegalArgumentException for alpha = 0");
75         } catch (IllegalArgumentException JavaDoc ex) {
76             // expected
77 }
78         try {
79             distribution.setBeta(0d);
80             fail("Expecting IllegalArgumentException for beta = 0");
81         } catch (IllegalArgumentException JavaDoc ex) {
82             // expected
83 }
84     }
85     
86     public void testProbabilities() throws Exception JavaDoc {
87         testProbability(-1.000, 4.0, 2.0, .0000);
88         testProbability(15.501, 4.0, 2.0, .9499);
89         testProbability(0.504, 4.0, 1.0, .0018);
90         testProbability(10.011, 1.0, 2.0, .9933);
91         testProbability(5.000, 2.0, 2.0, .7127);
92     }
93
94     public void testValues() throws Exception JavaDoc {
95         testValue(15.501, 4.0, 2.0, .9499);
96         testValue(0.504, 4.0, 1.0, .0018);
97         testValue(10.011, 1.0, 2.0, .9933);
98         testValue(5.000, 2.0, 2.0, .7127);
99     }
100
101     private void testProbability(double x, double a, double b, double expected) throws Exception JavaDoc {
102         DistributionFactory factory = DistributionFactory.newInstance();
103         GammaDistribution distribution = factory.createGammaDistribution( a, b );
104         double actual = distribution.cumulativeProbability(x);
105         assertEquals("probability for " + x, expected, actual, 10e-4);
106     }
107
108     private void testValue(double expected, double a, double b, double p) throws Exception JavaDoc {
109         DistributionFactory factory = DistributionFactory.newInstance();
110         GammaDistribution distribution = factory.createGammaDistribution( a, b );
111         double actual = distribution.inverseCumulativeProbability(p);
112         assertEquals("critical value for " + p, expected, actual, 10e-4);
113     }
114     
115     public void testInverseCumulativeProbabilityExtremes() throws Exception JavaDoc {
116         setInverseCumulativeTestPoints(new double[] {0, 1});
117         setInverseCumulativeTestValues(new double[] {0, Double.POSITIVE_INFINITY});
118         verifyInverseCumulativeProbabilities();
119     }
120 }
121
Popular Tags