/*
* 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;
/**
* Class CurveFitting defines various curve fitting algorithms inluding linear regression.
*
* This class cannot be subclassed or instantiated because all methods are static.
*
* @author Wolfgang Christian
*/
public class CurveFitting {
private CurveFitting() {} // prohibit instantiation because all methods are static
/**
* Computes the linear regression for the given data.
* @param xpoints double[]
* @param ypoints double[]
* @return Function the linear regression function
*/
public static Function linearRegression(double[] xpoints, double[] ypoints) {
double xBar_yBar = 0;
double xBar = 0;
double yBar = 0;
double x2Bar = 0;
double x = 0;
double y = 0;
for(int i = 0; i<xpoints.length; i++) {
x = xpoints[i];
y = ypoints[i];
xBar_yBar += x*y;
xBar += x;
yBar += y;
x2Bar += x*x;
}
int n = xpoints.length;
xBar_yBar = xBar_yBar/n;
xBar = xBar/n;
yBar = yBar/n;
x2Bar = x2Bar/n;
double deltaX2 = x2Bar-xBar*xBar;
final double m = (xBar_yBar-xBar*yBar)/deltaX2;
final double b = yBar-m*xBar;
return new Function() {
public double evaluate(double x) {
return m*x+b;
}
public String toString() {
return "linear regression: y(x) = "+m+"x + "+b; //$NON-NLS-1$ //$NON-NLS-2$
}
};
}
}
/*
* 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
*/