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18 package org.apache.commons.math4.legacy.analysis.function;
19
20 import org.apache.commons.math4.legacy.analysis.UnivariateFunction;
21 import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
22 import org.apache.commons.math4.legacy.exception.NoDataException;
23 import org.apache.commons.math4.legacy.exception.NonMonotonicSequenceException;
24 import org.apache.commons.math4.legacy.exception.NullArgumentException;
25 import org.junit.Assert;
26 import org.junit.Test;
27
28
29
30
31 public class StepFunctionTest {
32 private final double EPS = Math.ulp(1d);
33
34 @Test(expected=NullArgumentException.class)
35 public void testPreconditions1() {
36 new StepFunction(null, new double[] {0, -1, -2});
37 }
38
39 @Test(expected=NullArgumentException.class)
40 public void testPreconditions2() {
41 new StepFunction(new double[] {0, 1}, null);
42 }
43
44 @Test(expected=NoDataException.class)
45 public void testPreconditions3() {
46 new StepFunction(new double[] {0}, new double[] {});
47 }
48
49 @Test(expected=NoDataException.class)
50 public void testPreconditions4() {
51 new StepFunction(new double[] {}, new double[] {0});
52 }
53
54 @Test(expected=DimensionMismatchException.class)
55 public void testPreconditions5() {
56 new StepFunction(new double[] {0, 1}, new double[] {0, -1, -2});
57 }
58
59 @Test(expected=NonMonotonicSequenceException.class)
60 public void testPreconditions6() {
61 new StepFunction(new double[] {1, 0, 1}, new double[] {0, -1, -2});
62 }
63
64 @Test
65 public void testSomeValues() {
66 final double[] x = { -2, -0.5, 0, 1.9, 7.4, 21.3 };
67 final double[] y = { 4, -1, -5.5, 0.4, 5.8, 51.2 };
68
69 final UnivariateFunction f = new StepFunction(x, y);
70
71 Assert.assertEquals(4, f.value(Double.NEGATIVE_INFINITY), EPS);
72 Assert.assertEquals(4, f.value(-10), EPS);
73 Assert.assertEquals(-1, f.value(-0.4), EPS);
74 Assert.assertEquals(-5.5, f.value(0), EPS);
75 Assert.assertEquals(0.4, f.value(2), EPS);
76 Assert.assertEquals(5.8, f.value(10), EPS);
77 Assert.assertEquals(51.2, f.value(30), EPS);
78 Assert.assertEquals(51.2, f.value(Double.POSITIVE_INFINITY), EPS);
79 }
80
81 @Test
82 public void testEndpointBehavior() {
83 final double[] x = {0, 1, 2, 3};
84 final double[] xp = {-8, 1, 2, 3};
85 final double[] y = {1, 2, 3, 4};
86 final UnivariateFunction f = new StepFunction(x, y);
87 final UnivariateFunction fp = new StepFunction(xp, y);
88 Assert.assertEquals(f.value(-8), fp.value(-8), EPS);
89 Assert.assertEquals(f.value(-10), fp.value(-10), EPS);
90 Assert.assertEquals(f.value(0), fp.value(0), EPS);
91 Assert.assertEquals(f.value(0.5), fp.value(0.5), EPS);
92 for (int i = 0; i < x.length; i++) {
93 Assert.assertEquals(y[i], f.value(x[i]), EPS);
94 if (i > 0) {
95 Assert.assertEquals(y[i - 1], f.value(x[i] - 0.5), EPS);
96 } else {
97 Assert.assertEquals(y[0], f.value(x[i] - 0.5), EPS);
98 }
99 }
100 }
101
102 @Test
103 public void testHeaviside() {
104 final UnivariateFunction h = new StepFunction(new double[] {-1, 0},
105 new double[] {0, 1});
106
107 Assert.assertEquals(0, h.value(Double.NEGATIVE_INFINITY), 0);
108 Assert.assertEquals(0, h.value(-Double.MAX_VALUE), 0);
109 Assert.assertEquals(0, h.value(-2), 0);
110 Assert.assertEquals(0, h.value(-Double.MIN_VALUE), 0);
111 Assert.assertEquals(1, h.value(0), 0);
112 Assert.assertEquals(1, h.value(2), 0);
113 Assert.assertEquals(1, h.value(Double.POSITIVE_INFINITY), 0);
114 }
115 }