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Java example source code file (TriangularDistributionTest.java)

This example Java source code file (TriangularDistributionTest.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

override, realdistributionabstracttest, test, triangulardistribution, triangulardistributiontest

The TriangularDistributionTest.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.exception.NumberIsTooLargeException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.junit.Assert;
import org.junit.Test;

/**
 * Test cases for {@link TriangularDistribution}. See class javadoc for
 * {@link RealDistributionAbstractTest} for further details.
 */
public class TriangularDistributionTest extends RealDistributionAbstractTest {

    // --- Override tolerance -------------------------------------------------

    @Override
    public void setUp() {
        super.setUp();
        setTolerance(1e-4);
    }

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

    /**
     * Creates the default triangular distribution instance to use in tests.
     */
    @Override
    public TriangularDistribution makeDistribution() {
        // Left side 5 wide, right side 10 wide.
        return new TriangularDistribution(-3, 2, 12);
    }

    /**
     * Creates the default cumulative probability distribution test input
     * values.
     */
    @Override
    public double[] makeCumulativeTestPoints() {
        return new double[] { -3.0001,                 // below lower limit
                              -3.0,                    // at lower limit
                              -2.0, -1.0, 0.0, 1.0,    // on lower side
                              2.0,                     // at mode
                              3.0, 4.0, 10.0, 11.0,    // on upper side
                              12.0,                    // at upper limit
                              12.0001                  // above upper limit
                            };
    }

    /**
     * Creates the default cumulative probability density test expected values.
     */
    @Override
    public double[] makeCumulativeTestValues() {
        // Top at 2 / (b - a) = 2 / (12 - -3) = 2 / 15 = 7.5
        // Area left  = 7.5 * 5  * 0.5 = 18.75 (1/3 of the total area)
        // Area right = 7.5 * 10 * 0.5 = 37.5  (2/3 of the total area)
        // Area total = 18.75 + 37.5 = 56.25
        // Derivative left side = 7.5 / 5 = 1.5
        // Derivative right side = -7.5 / 10 = -0.75
        double third = 1 / 3.0;
        double left = 18.75;
        double area = 56.25;
        return new double[] { 0.0,
                              0.0,
                              0.75 / area, 3 / area, 6.75 / area, 12 / area,
                              third,
                              (left + 7.125) / area, (left + 13.5) / area,
                              (left + 36) / area, (left + 37.125) / area,
                              1.0,
                              1.0
                            };
    }

    /**
     * Creates the default inverse cumulative probability distribution test
     * input values.
     */
    @Override
    public double[] makeInverseCumulativeTestPoints() {
        // Exclude the points outside the limits, as they have cumulative
        // probability of zero and one, meaning the inverse returns the
        // limits and not the points outside the limits.
        double[] points = makeCumulativeTestValues();
        double[] points2 = new double[points.length-2];
        System.arraycopy(points, 1, points2, 0, points2.length);
        return points2;
        //return Arrays.copyOfRange(points, 1, points.length - 1);
    }

    /**
     * Creates the default inverse cumulative probability density test expected
     * values.
     */
    @Override
    public double[] makeInverseCumulativeTestValues() {
        // Exclude the points outside the limits, as they have cumulative
        // probability of zero and one, meaning the inverse returns the
        // limits and not the points outside the limits.
        double[] points = makeCumulativeTestPoints();
        double[] points2 = new double[points.length-2];
        System.arraycopy(points, 1, points2, 0, points2.length);
        return points2;
        //return Arrays.copyOfRange(points, 1, points.length - 1);
    }

    /** Creates the default probability density test expected values. */
    @Override
    public double[] makeDensityTestValues() {
        return new double[] { 0,
                              0,
                              2 / 75.0, 4 / 75.0, 6 / 75.0, 8 / 75.0,
                              10 / 75.0,
                              9 / 75.0, 8 / 75.0, 2 / 75.0, 1 / 75.0,
                              0,
                              0
                            };
    }

    //--- Additional test cases -----------------------------------------------

    /** Test lower bound getter. */
    @Test
    public void testGetLowerBound() {
        TriangularDistribution distribution = makeDistribution();
        Assert.assertEquals(-3.0, distribution.getSupportLowerBound(), 0);
    }

    /** Test upper bound getter. */
    @Test
    public void testGetUpperBound() {
        TriangularDistribution distribution = makeDistribution();
        Assert.assertEquals(12.0, distribution.getSupportUpperBound(), 0);
    }

    /** Test pre-condition for equal lower/upper limit. */
    @Test(expected=NumberIsTooLargeException.class)
    public void testPreconditions1() {
        new TriangularDistribution(0, 0, 0);
    }

    /** Test pre-condition for lower limit larger than upper limit. */
    @Test(expected=NumberIsTooLargeException.class)
    public void testPreconditions2() {
        new TriangularDistribution(1, 1, 0);
    }

    /** Test pre-condition for mode larger than upper limit. */
    @Test(expected=NumberIsTooLargeException.class)
    public void testPreconditions3() {
        new TriangularDistribution(0, 2, 1);
    }

    /** Test pre-condition for mode smaller than lower limit. */
    @Test(expected=NumberIsTooSmallException.class)
    public void testPreconditions4() {
        new TriangularDistribution(2, 1, 3);
    }

    /** Test mean/variance. */
    @Test
    public void testMeanVariance() {
        TriangularDistribution dist;

        dist = new TriangularDistribution(0, 0.5, 1.0);
        Assert.assertEquals(dist.getNumericalMean(), 0.5, 0);
        Assert.assertEquals(dist.getNumericalVariance(), 1 / 24.0, 0);

        dist = new TriangularDistribution(0, 1, 1);
        Assert.assertEquals(dist.getNumericalMean(), 2 / 3.0, 0);
        Assert.assertEquals(dist.getNumericalVariance(), 1 / 18.0, 0);

        dist = new TriangularDistribution(-3, 2, 12);
        Assert.assertEquals(dist.getNumericalMean(), 3 + (2 / 3.0), 0);
        Assert.assertEquals(dist.getNumericalVariance(), 175 / 18.0, 0);
    }
}

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