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17 package org.apache.commons.math.transform;
18
19 import org.apache.commons.math.analysis.*;
20 import org.apache.commons.math.complex.*;
21 import org.apache.commons.math.MathException;
22 import junit.framework.TestCase;
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31
32 public final class FastFourierTransformerTest extends TestCase {
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36
37 public void testAdHocData() {
38 FastFourierTransformer transformer = new FastFourierTransformer();
39 Complex result[]; double tolerance = 1E-12;
40
41 double x[] = {1.3, 2.4, 1.7, 4.1, 2.9, 1.7, 5.1, 2.7};
42 Complex y[] = {
43 new Complex(21.9, 0.0),
44 new Complex(-2.09497474683058, 1.91507575950825),
45 new Complex(-2.6, 2.7),
46 new Complex(-1.10502525316942, -4.88492424049175),
47 new Complex(0.1, 0.0),
48 new Complex(-1.10502525316942, 4.88492424049175),
49 new Complex(-2.6, -2.7),
50 new Complex(-2.09497474683058, -1.91507575950825)};
51
52 result = transformer.transform(x);
53 for (int i = 0; i < result.length; i++) {
54 assertEquals(y[i].getReal(), result[i].getReal(), tolerance);
55 assertEquals(y[i].getImaginary(), result[i].getImaginary(), tolerance);
56 }
57
58 result = transformer.inversetransform(y);
59 for (int i = 0; i < result.length; i++) {
60 assertEquals(x[i], result[i].getReal(), tolerance);
61 assertEquals(0.0, result[i].getImaginary(), tolerance);
62 }
63
64 double x2[] = {10.4, 21.6, 40.8, 13.6, 23.2, 32.8, 13.6, 19.2};
65 FastFourierTransformer.scaleArray(x2, 1.0 / Math.sqrt(x2.length));
66 Complex y2[] = y;
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68 result = transformer.transform2(y2);
69 for (int i = 0; i < result.length; i++) {
70 assertEquals(x2[i], result[i].getReal(), tolerance);
71 assertEquals(0.0, result[i].getImaginary(), tolerance);
72 }
73
74 result = transformer.inversetransform2(x2);
75 for (int i = 0; i < result.length; i++) {
76 assertEquals(y2[i].getReal(), result[i].getReal(), tolerance);
77 assertEquals(y2[i].getImaginary(), result[i].getImaginary(), tolerance);
78 }
79 }
80
81 public void test2DData() {
82 FastFourierTransformer transformer = new FastFourierTransformer();
83 double tolerance = 1E-12;
84 Complex[][] input = new Complex[][] {new Complex[] {new Complex(1, 0),
85 new Complex(2, 0)},
86 new Complex[] {new Complex(3, 1),
87 new Complex(4, 2)}};
88 Complex[][] goodOutput = new Complex[][] {new Complex[] {new Complex(5,
89 1.5), new Complex(-1, -.5)}, new Complex[] {new Complex(-2,
90 -1.5), new Complex(0, .5)}};
91 Complex[][] output = (Complex[][])transformer.mdfft(input, true);
92 Complex[][] output2 = (Complex[][])transformer.mdfft(output, false);
93
94 assertEquals(input.length, output.length);
95 assertEquals(input.length, output2.length);
96 assertEquals(input[0].length, output[0].length);
97 assertEquals(input[0].length, output2[0].length);
98 assertEquals(input[1].length, output[1].length);
99 assertEquals(input[1].length, output2[1].length);
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101 for (int i = 0; i < input.length; i++) {
102 for (int j = 0; j < input[0].length; j++) {
103 assertEquals(input[i][j].getImaginary(), output2[i][j].getImaginary(),
104 tolerance);
105 assertEquals(input[i][j].getReal(), output2[i][j].getReal(), tolerance);
106 assertEquals(goodOutput[i][j].getImaginary(), output[i][j].getImaginary(),
107 tolerance);
108 assertEquals(goodOutput[i][j].getReal(), output[i][j].getReal(), tolerance);
109 }
110 }
111 }
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116 public void testSinFunction() throws MathException {
117 UnivariateRealFunction f = new SinFunction();
118 FastFourierTransformer transformer = new FastFourierTransformer();
119 Complex result[]; int N = 1 << 8;
120 double min, max, tolerance = 1E-12;
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122 min = 0.0; max = 2.0 * Math.PI;
123 result = transformer.transform(f, min, max, N);
124 assertEquals(0.0, result[1].getReal(), tolerance);
125 assertEquals(-(N >> 1), result[1].getImaginary(), tolerance);
126 assertEquals(0.0, result[N-1].getReal(), tolerance);
127 assertEquals(N >> 1, result[N-1].getImaginary(), tolerance);
128 for (int i = 0; i < N-1; i += (i == 0 ? 2 : 1)) {
129 assertEquals(0.0, result[i].getReal(), tolerance);
130 assertEquals(0.0, result[i].getImaginary(), tolerance);
131 }
132
133 min = -Math.PI; max = Math.PI;
134 result = transformer.inversetransform(f, min, max, N);
135 assertEquals(0.0, result[1].getReal(), tolerance);
136 assertEquals(-0.5, result[1].getImaginary(), tolerance);
137 assertEquals(0.0, result[N-1].getReal(), tolerance);
138 assertEquals(0.5, result[N-1].getImaginary(), tolerance);
139 for (int i = 0; i < N-1; i += (i == 0 ? 2 : 1)) {
140 assertEquals(0.0, result[i].getReal(), tolerance);
141 assertEquals(0.0, result[i].getImaginary(), tolerance);
142 }
143 }
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147
148 public void testParameters() throws Exception {
149 UnivariateRealFunction f = new SinFunction();
150 FastFourierTransformer transformer = new FastFourierTransformer();
151
152 try {
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154 transformer.transform(f, 1, -1, 64);
155 fail("Expecting IllegalArgumentException - bad interval");
156 } catch (IllegalArgumentException ex) {
157
158 }
159 try {
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161 transformer.transform(f, -1, 1, 0);
162 fail("Expecting IllegalArgumentException - bad samples number");
163 } catch (IllegalArgumentException ex) {
164
165 }
166 try {
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168 transformer.transform(f, -1, 1, 100);
169 fail("Expecting IllegalArgumentException - bad samples number");
170 } catch (IllegalArgumentException ex) {
171
172 }
173 }
174 }