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 */ 017 018 package org.apache.commons.math.optimization.fitting; 019 020 import org.apache.commons.math.analysis.DifferentiableUnivariateRealFunction; 021 import org.apache.commons.math.util.FastMath; 022 023 /** Harmonic function of the form <code>f (t) = a cos (ω t + φ)</code>. 024 * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 ao??t 2010) $ 025 * @since 2.0 026 */ 027 public class HarmonicFunction implements DifferentiableUnivariateRealFunction { 028 029 /** Amplitude a. */ 030 private final double a; 031 032 /** Pulsation ω. */ 033 private final double omega; 034 035 /** Phase φ. */ 036 private final double phi; 037 038 /** Simple constructor. 039 * @param a amplitude 040 * @param omega pulsation 041 * @param phi phase 042 */ 043 public HarmonicFunction(double a, double omega, double phi) { 044 this.a = a; 045 this.omega = omega; 046 this.phi = phi; 047 } 048 049 /** {@inheritDoc} */ 050 public double value(double x) { 051 return a * FastMath.cos(omega * x + phi); 052 } 053 054 /** {@inheritDoc} */ 055 public HarmonicFunction derivative() { 056 return new HarmonicFunction(a * omega, omega, phi + FastMath.PI / 2); 057 } 058 059 /** Get the amplitude a. 060 * @return amplitude a; 061 */ 062 public double getAmplitude() { 063 return a; 064 } 065 066 /** Get the pulsation ω. 067 * @return pulsation ω 068 */ 069 public double getPulsation() { 070 return omega; 071 } 072 073 /** Get the phase φ. 074 * @return phase φ 075 */ 076 public double getPhase() { 077 return phi; 078 } 079 080 }