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 */
017package org.apache.commons.math4.transform;
018
019import java.util.function.DoubleUnaryOperator;
020import java.util.function.UnaryOperator;
021
022/**
023 * Real transforms.
024 */
025public interface RealTransform extends UnaryOperator<double[]> {
026    /**
027     * Returns the transform of the specified data set.
028     *
029     * @param f the data array to be transformed (signal).
030     * @return the transformed array (spectrum).
031     * @throws IllegalArgumentException if the transform cannot be performed.
032     */
033    @Override
034    double[] apply(double[] f);
035
036    /**
037     * Returns the transform of the specified function.
038     *
039     * @param f Function to be sampled and transformed.
040     * @param min Lower bound (inclusive) of the interval.
041     * @param max Upper bound (exclusive) of the interval.
042     * @param n Number of sample points.
043     * @return the result.
044     * @throws IllegalArgumentException if the transform cannot be performed.
045     */
046    default double[] apply(DoubleUnaryOperator f,
047                           double min,
048                           double max,
049                           int n) {
050        return apply(TransformUtils.sample(f, min, max, n));
051    }
052}