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 18 package org.apache.commons.math.optimization.fitting; 19 20 import org.apache.commons.math.analysis.DifferentiableUnivariateRealFunction; 21 22 /** Harmonic function of the form <code>f (t) = a cos (ω t + φ)</code>. 23 * @version $Revision: 786479 $ $Date: 2009-06-19 08:36:16 -0400 (Fri, 19 Jun 2009) $ 24 * @since 2.0 25 */ 26 public class HarmonicFunction implements DifferentiableUnivariateRealFunction { 27 28 /** Amplitude a. */ 29 private final double a; 30 31 /** Pulsation ω. */ 32 private final double omega; 33 34 /** Phase φ. */ 35 private final double phi; 36 37 /** Simple constructor. 38 * @param a amplitude 39 * @param omega pulsation 40 * @param phi phase 41 */ 42 public HarmonicFunction(double a, double omega, double phi) { 43 this.a = a; 44 this.omega = omega; 45 this.phi = phi; 46 } 47 48 /** {@inheritDoc} */ 49 public double value(double x) { 50 return a * Math.cos(omega * x + phi); 51 } 52 53 /** {@inheritDoc} */ 54 public HarmonicFunction derivative() { 55 return new HarmonicFunction(a * omega, omega, phi + Math.PI / 2); 56 } 57 58 /** Get the amplitude a. 59 * @return amplitude a; 60 */ 61 public double getAmplitude() { 62 return a; 63 } 64 65 /** Get the pulsation ω. 66 * @return pulsation ω 67 */ 68 public double getPulsation() { 69 return omega; 70 } 71 72 /** Get the phase φ. 73 * @return phase φ 74 */ 75 public double getPhase() { 76 return phi; 77 } 78 79 }