/*
* 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.math4.analysis.function;
import org.apache.commons.math4.analysis.UnivariateFunction;
import org.apache.commons.math4.analysis.function.StepFunction;
import org.apache.commons.math4.exception.DimensionMismatchException;
import org.apache.commons.math4.exception.NoDataException;
import org.apache.commons.math4.exception.NonMonotonicSequenceException;
import org.apache.commons.math4.exception.NullArgumentException;
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);
}
}