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Java example source code file (StepFunctionTest.java)

This example Java source code file (StepFunctionTest.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

eps, stepfunction, stepfunctiontest, test, univariatefunction

The StepFunctionTest.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.analysis.function;

import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.NonMonotonicSequenceException;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.exception.NoDataException;

import org.junit.Assert;
import org.junit.Test;

/**
 * Test for class {@link StepFunction}.
 */
public class StepFunctionTest {
    private final double EPS = Math.ulp(1d);

    @Test(expected=NullArgumentException.class)
    public void testPreconditions1() {
        new StepFunction(null, new double[] {0, -1, -2});
    }

    @Test(expected=NullArgumentException.class)
    public void testPreconditions2() {
        new StepFunction(new double[] {0, 1}, null);
    }

    @Test(expected=NoDataException.class)
    public void testPreconditions3() {
        new StepFunction(new double[] {0}, new double[] {});
    }

    @Test(expected=NoDataException.class)
    public void testPreconditions4() {
        new StepFunction(new double[] {}, new double[] {0});
    }

    @Test(expected=DimensionMismatchException.class)
    public void testPreconditions5() {
        new StepFunction(new double[] {0, 1}, new double[] {0, -1, -2});
    }

    @Test(expected=NonMonotonicSequenceException.class)
    public void testPreconditions6() {
        new StepFunction(new double[] {1, 0, 1}, new double[] {0, -1, -2});
    }

    @Test
    public void testSomeValues() {
        final double[] x = { -2, -0.5, 0, 1.9, 7.4, 21.3 };
        final double[] y = { 4, -1, -5.5, 0.4, 5.8, 51.2 };

        final UnivariateFunction f = new StepFunction(x, y);

        Assert.assertEquals(4, f.value(Double.NEGATIVE_INFINITY), EPS);
        Assert.assertEquals(4, f.value(-10), EPS);
        Assert.assertEquals(-1, f.value(-0.4), EPS);
        Assert.assertEquals(-5.5, f.value(0), EPS);
        Assert.assertEquals(0.4, f.value(2), EPS);
        Assert.assertEquals(5.8, f.value(10), EPS);
        Assert.assertEquals(51.2, f.value(30), EPS);
        Assert.assertEquals(51.2, f.value(Double.POSITIVE_INFINITY), EPS);
    }

    @Test
    public void testEndpointBehavior() {
        final double[] x = {0, 1, 2, 3};
        final double[] xp = {-8, 1, 2, 3};
        final double[] y = {1, 2, 3, 4};
        final UnivariateFunction f = new StepFunction(x, y);
        final UnivariateFunction fp = new StepFunction(xp, y);
        Assert.assertEquals(f.value(-8), fp.value(-8), EPS);
        Assert.assertEquals(f.value(-10), fp.value(-10), EPS);
        Assert.assertEquals(f.value(0), fp.value(0), EPS);
        Assert.assertEquals(f.value(0.5), fp.value(0.5), EPS);
        for (int i = 0; i < x.length; i++) {
           Assert.assertEquals(y[i], f.value(x[i]), EPS);
           if (i > 0) {
               Assert.assertEquals(y[i - 1], f.value(x[i] - 0.5), EPS);
           } else {
               Assert.assertEquals(y[0], f.value(x[i] - 0.5), EPS);
           }
        }
    }

    @Test
    public void testHeaviside() {
        final UnivariateFunction h = new StepFunction(new double[] {-1, 0},
                                                          new double[] {0, 1});

        Assert.assertEquals(0, h.value(Double.NEGATIVE_INFINITY), 0);
        Assert.assertEquals(0, h.value(-Double.MAX_VALUE), 0);
        Assert.assertEquals(0, h.value(-2), 0);
        Assert.assertEquals(0, h.value(-Double.MIN_VALUE), 0);
        Assert.assertEquals(1, h.value(0), 0);
        Assert.assertEquals(1, h.value(2), 0);
        Assert.assertEquals(1, h.value(Double.POSITIVE_INFINITY), 0);
    }
}

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