001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math.transform;
018
019 import org.apache.commons.math.analysis.*;
020 import org.apache.commons.math.MathException;
021 import junit.framework.TestCase;
022
023 /**
024 * Testcase for fast cosine transformer.
025 * <p>
026 * FCT algorithm is exact, the small tolerance number is used only
027 * to account for round-off errors.
028 *
029 * @version $Revision: 764769 $ $Date: 2009-04-14 09:13:54 -0400 (Tue, 14 Apr 2009) $
030 */
031 public final class FastCosineTransformerTest extends TestCase {
032
033 /**
034 * Test of transformer for the ad hoc data.
035 */
036 public void testAdHocData() {
037 FastCosineTransformer transformer = new FastCosineTransformer();
038 double result[], tolerance = 1E-12;
039
040 double x[] = { 0.0, 1.0, 4.0, 9.0, 16.0, 25.0, 36.0, 49.0, 64.0 };
041 double y[] = { 172.0, -105.096569476353, 27.3137084989848,
042 -12.9593152353742, 8.0, -5.78585076868676,
043 4.68629150101524, -4.15826451958632, 4.0 };
044
045 result = transformer.transform(x);
046 for (int i = 0; i < result.length; i++) {
047 assertEquals(y[i], result[i], tolerance);
048 }
049
050 result = transformer.inversetransform(y);
051 for (int i = 0; i < result.length; i++) {
052 assertEquals(x[i], result[i], tolerance);
053 }
054
055 FastFourierTransformer.scaleArray(x, Math.sqrt(0.5 * (x.length-1)));
056
057 result = transformer.transform2(y);
058 for (int i = 0; i < result.length; i++) {
059 assertEquals(x[i], result[i], tolerance);
060 }
061
062 result = transformer.inversetransform2(x);
063 for (int i = 0; i < result.length; i++) {
064 assertEquals(y[i], result[i], tolerance);
065 }
066 }
067
068 /**
069 * Test of transformer for the sine function.
070 */
071 public void testSinFunction() throws MathException {
072 UnivariateRealFunction f = new SinFunction();
073 FastCosineTransformer transformer = new FastCosineTransformer();
074 double min, max, result[], tolerance = 1E-12; int N = 9;
075
076 double expected[] = { 0.0, 3.26197262739567, 0.0,
077 -2.17958042710327, 0.0, -0.648846697642915,
078 0.0, -0.433545502649478, 0.0 };
079 min = 0.0; max = 2.0 * Math.PI * N / (N-1);
080 result = transformer.transform(f, min, max, N);
081 for (int i = 0; i < N; i++) {
082 assertEquals(expected[i], result[i], tolerance);
083 }
084
085 min = -Math.PI; max = Math.PI * (N+1) / (N-1);
086 result = transformer.transform(f, min, max, N);
087 for (int i = 0; i < N; i++) {
088 assertEquals(-expected[i], result[i], tolerance);
089 }
090 }
091
092 /**
093 * Test of parameters for the transformer.
094 */
095 public void testParameters() throws Exception {
096 UnivariateRealFunction f = new SinFunction();
097 FastCosineTransformer transformer = new FastCosineTransformer();
098
099 try {
100 // bad interval
101 transformer.transform(f, 1, -1, 65);
102 fail("Expecting IllegalArgumentException - bad interval");
103 } catch (IllegalArgumentException ex) {
104 // expected
105 }
106 try {
107 // bad samples number
108 transformer.transform(f, -1, 1, 1);
109 fail("Expecting IllegalArgumentException - bad samples number");
110 } catch (IllegalArgumentException ex) {
111 // expected
112 }
113 try {
114 // bad samples number
115 transformer.transform(f, -1, 1, 64);
116 fail("Expecting IllegalArgumentException - bad samples number");
117 } catch (IllegalArgumentException ex) {
118 // expected
119 }
120 }
121 }