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Java example source code file (ExponentialDistributionTest.java)

This example Java source code file (ExponentialDistributionTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

exponentialdistribution, exponentialdistributiontest, override, realdistributionabstracttest, suppresswarnings, test

The ExponentialDistributionTest.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math3.distribution;

import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.Precision;
import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.junit.Assert;
import org.junit.Test;

/**
 * Test cases for ExponentialDistribution.
 * Extends ContinuousDistributionAbstractTest.  See class javadoc for
 * ContinuousDistributionAbstractTest for details.
 *
 */
public class ExponentialDistributionTest extends RealDistributionAbstractTest {

    // --------------------- Override tolerance  --------------
    @Override
    public void setUp() {
        super.setUp();
        setTolerance(1E-9);
    }

    //-------------- Implementations for abstract methods -----------------------

    /** Creates the default continuous distribution instance to use in tests. */
    @Override
    public ExponentialDistribution makeDistribution() {
        return new ExponentialDistribution(5.0);
    }

    /** Creates the default cumulative probability distribution test input values */
    @Override
    public double[] makeCumulativeTestPoints() {
        // quantiles computed using R version 2.9.2
        return new double[] {0.00500250166792, 0.0502516792675, 0.126589039921, 0.256466471938,
                0.526802578289, 34.5387763949, 23.0258509299, 18.4443972706, 14.9786613678, 11.5129254650};
    }

    /** Creates the default cumulative probability density test expected values */
    @Override
    public double[] makeCumulativeTestValues() {
        return new double[] {0.001, 0.01, 0.025, 0.05, 0.1, 0.999,
                0.990, 0.975, 0.950, 0.900};
    }

    /** Creates the default probability density test expected values */
    @Override
    public double[] makeDensityTestValues() {
        return new double[] {0.1998, 0.198, 0.195, 0.19, 0.18, 0.000200000000000,
                0.00200000000002, 0.00499999999997, 0.00999999999994, 0.0199999999999};
    }

    //------------ Additional tests -------------------------------------------

    @Test
    public void testCumulativeProbabilityExtremes() {
        setCumulativeTestPoints(new double[] {-2, 0});
        setCumulativeTestValues(new double[] {0, 0});
        verifyCumulativeProbabilities();
    }

    @Test
    public void testInverseCumulativeProbabilityExtremes() {
         setInverseCumulativeTestPoints(new double[] {0, 1});
         setInverseCumulativeTestValues(new double[] {0, Double.POSITIVE_INFINITY});
         verifyInverseCumulativeProbabilities();
    }

    @Test
    public void testCumulativeProbability2() {
        @SuppressWarnings("deprecation")
        double actual = getDistribution().cumulativeProbability(0.25, 0.75);
        Assert.assertEquals(0.0905214, actual, 10e-4);
    }

    @Test
    public void testDensity() {
        ExponentialDistribution d1 = new ExponentialDistribution(1);
        Assert.assertTrue(Precision.equals(0.0, d1.density(-1e-9), 1));
        Assert.assertTrue(Precision.equals(1.0, d1.density(0.0), 1));
        Assert.assertTrue(Precision.equals(0.0, d1.density(1000.0), 1));
        Assert.assertTrue(Precision.equals(FastMath.exp(-1), d1.density(1.0), 1));
        Assert.assertTrue(Precision.equals(FastMath.exp(-2), d1.density(2.0), 1));

        ExponentialDistribution d2 = new ExponentialDistribution(3);
        Assert.assertTrue(Precision.equals(1/3.0, d2.density(0.0), 1));
        // computed using  print(dexp(1, rate=1/3), digits=10) in R 2.5
        Assert.assertEquals(0.2388437702, d2.density(1.0), 1e-8);

        // computed using  print(dexp(2, rate=1/3), digits=10) in R 2.5
        Assert.assertEquals(0.1711390397, d2.density(2.0), 1e-8);
    }

    @Test
    public void testMeanAccessors() {
        ExponentialDistribution distribution = (ExponentialDistribution) getDistribution();
        Assert.assertEquals(5d, distribution.getMean(), Double.MIN_VALUE);
    }

    @Test(expected=NotStrictlyPositiveException.class)
    public void testPreconditions() {
        new ExponentialDistribution(0);
    }

    @Test
    public void testMoments() {
        final double tol = 1e-9;
        ExponentialDistribution dist;

        dist = new ExponentialDistribution(11d);
        Assert.assertEquals(dist.getNumericalMean(), 11d, tol);
        Assert.assertEquals(dist.getNumericalVariance(), 11d * 11d, tol);

        dist = new ExponentialDistribution(10.5d);
        Assert.assertEquals(dist.getNumericalMean(), 10.5d, tol);
        Assert.assertEquals(dist.getNumericalVariance(), 10.5d * 10.5d, tol);
    }
}

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