/*
* LeastSquaresFitMethod.java
*
* Created on August 15, 2002, 4:38 PM
*/
package hep.aida.ref.fitter.fitmethod;
import hep.aida.IFunction;
import hep.aida.IModelFunction;
import hep.aida.dev.IDevFitDataIterator;
import hep.aida.ext.IFitMethod;
/**
*
* @author The AIDA team @ SLAC.
*
*/
public class LeastSquaresFitMethod extends AbstractFitMethod {
private static String[] names = new String[]{"leastsquares","ls"};
public LeastSquaresFitMethod() {
super(IFitMethod.BINNED_FIT, names);
}
public double evaluateSumElement(IDevFitDataIterator dataIter, IFunction function) {
return Math.pow( dataIter.value() - function.value( dataIter.vars() ) , 2);
}
public double[] evaluateGradientSumElement(IDevFitDataIterator dataIter, IFunction function) {
double f = function.value( dataIter.vars() );
double[] der = ((IModelFunction)function).parameterGradient( dataIter.vars() );
double[] newDer = new double[der.length];
double val = dataIter.value();
double d = (val-f);
double c = -2*d;
for ( int i = 0; i < der.length; i++ )
newDer[i] = der[i]*c;
return newDer;
}
}