Hi Yiqun, Have a look at TMinuit::SetObjectFit and TMinuit::GetObjectFit with which you can set and retrieve apointer to a class that inherits from TObject. In this class you could define data points and other fit information. Eddy --- Yiqun Wang <yqwang@rcf.rhic.bnl.gov> wrote: > Hi, ROOTers: > > I have a question on using TMinuit. I read the > tutorial "Ifit.C", but it > did not answer my question. I am using ROOT 3.10.00 > self-compiled on > Mandrake 9.1. > > In "Ifit.C", the data points "Float_t > z[5],x[5],y[5],errorz[5];" are > global variables. This is understandable, since > "void fcn(Int_t &npar, > Double_t *gin, Double_t &f, Double_t *par, Int_t > iflag)" has not idea what > data points to use beforehand. However, this is > ugly, not particularly > safe. > > Now suppose I want to make a custom fitter for my > own class. Data points > will come from the members of the class (actually I > will reload the data > members every event, use the fitter, and write fit > result to a tree). Can > I call "TMinuit::SetFCN(...)" on a memeber function > "void fcn(Int_t &npar, > Double_t *gin, Double_t &f, Double_t *par, Int_t > iflag)" (so it knows the > member data, without the need to make the data > global)? Is this possible? > Or there is a better solution? > > Thanks in advance! > > Yiqun Wang > >
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