/*
* Open Source Physics software is free software as described near the bottom of this code file.
*
* For additional information and documentation on Open Source Physics please see:
* <http://www.opensourcephysics.org/>
*/
package org.opensourcephysics.numerics.specialfunctions;
import java.util.ArrayList;
import org.opensourcephysics.numerics.Polynomial;
/**
* Chebyshev defines Chebyshev polynomials Tn(x) and Un(x) using
* the well known recurrence relationships. The information needed for this class
* was gained from Alan Jeffrey's Handbook of Mathematical Formulas
* and Integrals, 3rd Edition pages 290-295. Chebyshev polynomials
* are used to solve differential equations of second order, hence why
* we have two different types.
*
* This code is based on the Open Source Physics class for Hermite polynomials.
*
* @author Nick Dovidio
* @version 1.0
*/
public class Chebyshev {
static final ArrayList<Polynomial> chebyshevTList; //Stores Tn functions
static final ArrayList<Polynomial> chebyshevUList; //Stores Un functions
private Chebyshev() {}
/**
* This method returns the nth polynomial of type T. If it has already been calculated
* it just returns it from the list. If we have not calculated it uses
* the recursion relationship to calculate based off of the prior
* polynomials.
*/
public static synchronized Polynomial getPolynomialT(int n) {
if(n<0) {
throw new IllegalArgumentException(Messages.getString("Chebyshev.neg_degree")); //$NON-NLS-1$
}
if(n<chebyshevTList.size()) {
return chebyshevTList.get(n);
}
Polynomial part1 = new Polynomial(new double[] {0, (2.0)});
Polynomial p = part1.multiply(getPolynomialT(n-1)).subtract(getPolynomialT(n-2));
chebyshevTList.add(p);
return p;
}
/**
* This method returns the nth polynomial of type U. If it has already been calculated
* it just returns it from the list. If we have not calculated it uses
* the recursion relationship to calculate based off of the prior
* polynomials.
*/
public static synchronized Polynomial getPolynomialU(int n) {
if(n<chebyshevUList.size()) {
return chebyshevUList.get(n);
}
Polynomial part1 = new Polynomial(new double[] {0, (2.0)});
Polynomial p = part1.multiply(getPolynomialU(n-1)).subtract(getPolynomialU(n-2));
chebyshevUList.add(p);
return p;
}
/**
* Here we used a static initialization list to calculate the first two
* values needed for our recursive relationships.
*/
static {
chebyshevTList = new ArrayList<Polynomial>();
chebyshevUList = new ArrayList<Polynomial>();
Polynomial p = new Polynomial(new double[] {1.0});
chebyshevTList.add(p);
chebyshevUList.add(p);
p = new Polynomial(new double[] {0, 1.0});
chebyshevTList.add(p);
p = new Polynomial(new double[] {0, 2.0});
chebyshevUList.add(p);
}
}
/*
* Open Source Physics software is free software; you can redistribute
* it and/or modify it under the terms of the GNU General Public License (GPL) as
* published by the Free Software Foundation; either version 2 of the License,
* or(at your option) any later version.
* Code that uses any portion of the code in the org.opensourcephysics package
* or any subpackage (subdirectory) of this package must must also be be released
* under the GNU GPL license.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston MA 02111-1307 USA
* or view the license online at http://www.gnu.org/copyleft/gpl.html
*
* Copyright (c) 2007 The Open Source Physics project
* http://www.opensourcephysics.org
*/