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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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package org.apache.commons.math.optimization.fitting;
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import org.apache.commons.math.analysis.DifferentiableUnivariateRealFunction;
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/** Harmonic function of the form <code>f (t) = a cos (ω t + φ)</code>.
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* @version $Revision: 786479 $ $Date: 2009-06-19 08:36:16 -0400 (Fri, 19 Jun 2009) $
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public class HarmonicFunction implements DifferentiableUnivariateRealFunction {
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private final double a;
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/** Pulsation ω. */
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private final double omega;
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private final double phi;
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/** Simple constructor.
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* @param omega pulsation
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public HarmonicFunction(double a, double omega, double phi) {
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public double value(double x) {
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return a * Math.cos(omega * x + phi);
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public HarmonicFunction derivative() {
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return new HarmonicFunction(a * omega, omega, phi + Math.PI / 2);
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/** Get the amplitude a.
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* @return amplitude a;
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public double getAmplitude() {
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/** Get the pulsation ω.
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* @return pulsation ω
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public double getPulsation() {
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/** Get the phase φ.
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public double getPhase() {