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.transform;
18
19 import java.util.function.DoubleUnaryOperator;
20 import java.util.function.UnaryOperator;
21
22 import org.apache.commons.numbers.complex.Complex;
23
24 /**
25 * {@link Complex} transform.
26 * <p>
27 * Such transforms include {@link FastSineTransform sine transform},
28 * {@link FastCosineTransform cosine transform} or {@link
29 * FastHadamardTransform Hadamard transform}.
30 */
31 public interface ComplexTransform extends UnaryOperator<Complex[]> {
32 /**
33 * Returns the transform of the specified data set.
34 *
35 * @param f the data array to be transformed (signal).
36 * @return the transformed array (spectrum).
37 * @throws IllegalArgumentException if the transform cannot be performed.
38 */
39 Complex[] apply(Complex[] f);
40
41 /**
42 * Returns the transform of the specified data set.
43 *
44 * @param f the data array to be transformed (signal).
45 * @return the transformed array (spectrum).
46 * @throws IllegalArgumentException if the transform cannot be performed.
47 */
48 Complex[] apply(double[] f);
49
50 /**
51 * Returns the transform of the specified function.
52 *
53 * @param f Function to be sampled and transformed.
54 * @param min Lower bound (inclusive) of the interval.
55 * @param max Upper bound (exclusive) of the interval.
56 * @param n Number of sample points.
57 * @return the result.
58 * @throws IllegalArgumentException if the transform cannot be performed.
59 */
60 default Complex[] apply(DoubleUnaryOperator f,
61 double min,
62 double max,
63 int n) {
64 return apply(TransformUtils.sample(f, min, max, n));
65 }
66 }