    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  package org.apache.commons.math.distribution;
    17
    18  /***
    19   * Test cases for ExponentialDistribution.
    20   * Extends ContinuousDistributionAbstractTest.  See class javadoc for
    21   * ContinuousDistributionAbstractTest for details.
    22   *
    23   * @version $Revision: 1.15 $ $Date: 2004/06/06 16:39:06 $
    24   */
    25  public class ExponentialDistributionTest extends ContinuousDistributionAbstractTest {
    26
    27      /***
    28       * Constructor for ChiSquareDistributionTest.
    29       * @param name
    30       */
    31      public ExponentialDistributionTest(String name) {
    32          super(name);
    33      }
    34
    35      //-------------- Implementations for abstract methods -----------------------
    36
    37      /*** Creates the default continuous distribution instance to use in tests. */
    38      public ContinuousDistribution makeDistribution() {
    39          return DistributionFactory.newInstance().createExponentialDistribution(5.0);
    40      }
    41
    42      /*** Creates the default cumulative probability distribution test input values */
    43      public double[] makeCumulativeTestPoints() {
    44          // quantiles computed using R version 1.8.1 (linux version)
    45          return new double[] {0.005002502d, 0.05025168d, 0.1265890d, 0.2564665d, 0.5268026d,
    46                  34.53878d, 23.02585d, 18.44440d, 14.97866d, 11.51293d};
    47      }
    48
    49      /*** Creates the default cumulative probability density test expected values */
    50      public double[] makeCumulativeTestValues() {
    51          return new double[] {0.001d, 0.01d, 0.025d, 0.05d, 0.1d, 0.999d,
    52                  0.990d, 0.975d, 0.950d, 0.900d};
    53      }
    54
    55      //------------ Additional tests -------------------------------------------
    56
    57      public void testCumulativeProbabilityExtremes() throws Exception {
    58          setCumulativeTestPoints(new double[] {-2, 0});
    59          setCumulativeTestValues(new double[] {0, 0});
    60          verifyCumulativeProbabilities();
    61      }
    62
    63      public void testInverseCumulativeProbabilityExtremes() throws Exception {
    64           setInverseCumulativeTestPoints(new double[] {0, 1});
    65           setInverseCumulativeTestValues(new double[] {0, Double.POSITIVE_INFINITY});
    66           verifyInverseCumulativeProbabilities();
    67      }
    68
    69      public void testCumulativeProbability2() throws Exception {
    70          double actual = getDistribution().cumulativeProbability(0.25, 0.75);
    71          assertEquals(0.0905214, actual, 10e-4);
    72      }
    73
    74      public void testMeanAccessors() {
    75          ExponentialDistribution distribution = (ExponentialDistribution) getDistribution();
    76          assertEquals(5d, distribution.getMean(), Double.MIN_VALUE);
    77          distribution.setMean(2d);
    78          assertEquals(2d, distribution.getMean(), Double.MIN_VALUE);
    79          try {
    80              distribution.setMean(0);
    81              fail("Expecting IllegalArgumentException for 0 mean");
    82          } catch (IllegalArgumentException ex) {
    83              // expected
    84          }
    85      }
    86
    87  }