Home | History | Annotate | Download | only in fitting 
      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 import org.apache.commons.math.util.FastMath;
     22 
     23 /** Harmonic function of the form <code>f (t) = a cos (&omega; t + &phi;)</code>.
     24  * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 aot 2010) $
     25  * @since 2.0
     26  */
     27 public class HarmonicFunction implements DifferentiableUnivariateRealFunction {
     28 
     29     /** Amplitude a. */
     30     private final double a;
     31 
     32     /** Pulsation &omega;. */
     33     private final double omega;
     34 
     35     /** Phase &phi;. */
     36     private final double phi;
     37 
     38     /** Simple constructor.
     39      * @param a amplitude
     40      * @param omega pulsation
     41      * @param phi phase
     42      */
     43     public HarmonicFunction(double a, double omega, double phi) {
     44         this.a     = a;
     45         this.omega = omega;
     46         this.phi   = phi;
     47     }
     48 
     49     /** {@inheritDoc} */
     50     public double value(double x) {
     51         return a * FastMath.cos(omega * x + phi);
     52     }
     53 
     54     /** {@inheritDoc} */
     55     public HarmonicFunction derivative() {
     56         return new HarmonicFunction(a * omega, omega, phi + FastMath.PI / 2);
     57     }
     58 
     59     /** Get the amplitude a.
     60      * @return amplitude a;
     61      */
     62     public double getAmplitude() {
     63         return a;
     64     }
     65 
     66     /** Get the pulsation &omega;.
     67      * @return pulsation &omega;
     68      */
     69     public double getPulsation() {
     70         return omega;
     71     }
     72 
     73     /** Get the phase &phi;.
     74      * @return phase &phi;
     75      */
     76     public double getPhase() {
     77         return phi;
     78     }
     79 
     80 }
     81