1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math4.legacy.stat.descriptive.moment;
18
19 import org.apache.commons.math4.legacy.stat.descriptive.StorelessUnivariateStatisticAbstractTest;
20 import org.apache.commons.math4.legacy.stat.descriptive.UnivariateStatistic;
21 import org.junit.Assert;
22 import org.junit.Test;
23
24 /**
25 * Test cases for the {@link UnivariateStatistic} class.
26 *
27 */
28 public class SkewnessTest extends StorelessUnivariateStatisticAbstractTest{
29
30 protected Skewness stat;
31
32 /**
33 * {@inheritDoc}
34 */
35 @Override
36 public UnivariateStatistic getUnivariateStatistic() {
37 return new Skewness();
38 }
39
40 /**
41 * {@inheritDoc}
42 */
43 @Override
44 public double expectedValue() {
45 return this.skew;
46 }
47
48 /**
49 * Make sure Double.NaN is returned iff n < 3
50 */
51 @Test
52 public void testNaN() {
53 Skewness skew = new Skewness();
54 Assert.assertTrue(Double.isNaN(skew.getResult()));
55 skew.increment(1d);
56 Assert.assertTrue(Double.isNaN(skew.getResult()));
57 skew.increment(1d);
58 Assert.assertTrue(Double.isNaN(skew.getResult()));
59 skew.increment(1d);
60 Assert.assertFalse(Double.isNaN(skew.getResult()));
61 }
62
63 @Test
64 public void testZeroSkewness() {
65 final double[] values = {2, 2, 2, 2};
66 Assert.assertEquals(0, new Skewness().evaluate(values), 0.0);
67 }
68 }