FitMethodFunction class Interface for objective functions (like chi2 and likelihood used in the fit) In addition to normal function interface provide interface for calculating each data contrinution to the function which is required by some algorithm (like Fumili) @ingroup FitMethodFunc
Number of dimension (parameters) . From IGenMultiFunction interface
{ return fNDim; }
method returning the data i-th contribution to the fit objective function
For example the residual for the least square functions or the pdf element for the
likelihood functions.
Estimating eventually also the gradient of the data element if the passed pointer is not null
return the number of data points used in evaluating the function
{ return fNPoints; }
return the total number of function calls (overrided if needed)
{ return fNCalls; }