1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math.distribution;
18
19 /**
20 * Test cases for ExponentialDistribution.
21 * Extends ContinuousDistributionAbstractTest. See class javadoc for
22 * ContinuousDistributionAbstractTest for details.
23 *
24 * @version $Revision: 545192 $ $Date: 2007-06-07 07:35:04 -0700 (Thu, 07 Jun 2007) $
25 */
26 public class ExponentialDistributionTest extends ContinuousDistributionAbstractTest {
27
28 /**
29 * Constructor for ExponentialDistributionTest.
30 * @param name
31 */
32 public ExponentialDistributionTest(String 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 new ExponentialDistributionImpl(5.0);
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[] {0.005002502d, 0.05025168d, 0.1265890d, 0.2564665d, 0.5268026d,
47 34.53878d, 23.02585d, 18.44440d, 14.97866d, 11.51293d};
48 }
49
50 /** Creates the default cumulative probability density test expected values */
51 public double[] makeCumulativeTestValues() {
52 return new double[] {0.001d, 0.01d, 0.025d, 0.05d, 0.1d, 0.999d,
53 0.990d, 0.975d, 0.950d, 0.900d};
54 }
55
56 //------------ Additional tests -------------------------------------------
57
58 public void testCumulativeProbabilityExtremes() throws Exception {
59 setCumulativeTestPoints(new double[] {-2, 0});
60 setCumulativeTestValues(new double[] {0, 0});
61 verifyCumulativeProbabilities();
62 }
63
64 public void testInverseCumulativeProbabilityExtremes() throws Exception {
65 setInverseCumulativeTestPoints(new double[] {0, 1});
66 setInverseCumulativeTestValues(new double[] {0, Double.POSITIVE_INFINITY});
67 verifyInverseCumulativeProbabilities();
68 }
69
70 public void testCumulativeProbability2() throws Exception {
71 double actual = getDistribution().cumulativeProbability(0.25, 0.75);
72 assertEquals(0.0905214, actual, 10e-4);
73 }
74
75 public void testMeanAccessors() {
76 ExponentialDistribution distribution = (ExponentialDistribution) getDistribution();
77 assertEquals(5d, distribution.getMean(), Double.MIN_VALUE);
78 distribution.setMean(2d);
79 assertEquals(2d, distribution.getMean(), Double.MIN_VALUE);
80 try {
81 distribution.setMean(0);
82 fail("Expecting IllegalArgumentException for 0 mean");
83 } catch (IllegalArgumentException ex) {
84 // expected
85 }
86 }
87
88 }