org.apache.commons.math.optimization.fitting.HarmonicFunction Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math.optimization.fitting;
import org.apache.commons.math.analysis.DifferentiableUnivariateRealFunction;
import org.apache.commons.math.util.FastMath;
/** Harmonic function of the form f (t) = a cos (ω t + φ).
* @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 août 2010) $
* @since 2.0
*/
public class HarmonicFunction implements DifferentiableUnivariateRealFunction {
/** Amplitude a. */
private final double a;
/** Pulsation ω. */
private final double omega;
/** Phase φ. */
private final double phi;
/** Simple constructor.
* @param a amplitude
* @param omega pulsation
* @param phi phase
*/
public HarmonicFunction(double a, double omega, double phi) {
this.a = a;
this.omega = omega;
this.phi = phi;
}
/** {@inheritDoc} */
public double value(double x) {
return a * FastMath.cos(omega * x + phi);
}
/** {@inheritDoc} */
public HarmonicFunction derivative() {
return new HarmonicFunction(a * omega, omega, phi + FastMath.PI / 2);
}
/** Get the amplitude a.
* @return amplitude a;
*/
public double getAmplitude() {
return a;
}
/** Get the pulsation ω.
* @return pulsation ω
*/
public double getPulsation() {
return omega;
}
/** Get the phase φ.
* @return phase φ
*/
public double getPhase() {
return phi;
}
}