[ROOT] User specified fitting algorithm

From: Aihong Tang (aihong@cnr.physics.kent.edu)
Date: Sat Jul 01 2000 - 03:43:12 MEST 

Hi,

The documentation of TGraph::Fit says:

option="U" Use a User specified fitting algorithm (via SetFCN)

   =============================
  By default the fitting function GraphFitChisquare is used.
  To specify a User defined fitting function, specify option "U" and
  call the following functions:
    TVirtualFitter::Fitter(mygraph)->SetFCN(MyFittingFunction)
  where MyFittingFunction is of type:
  extern void MyFittingFunction(Int_t &npar, Double_t *gin, Double_t &f,
Double_t *u, Int_t flag);            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~

But it is not clear to me, what does the arguments of MyFittingFunction
mean? How does it work?  Is there an example showing how to customize
TGraph::Fitting?


Thanks!

Aihong

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