[ROOT] TH2F - TF2

From: Michael Wiesmann (wiesmann@e18.physik.tu-muenchen.de)
Date: Thu Jun 26 2003 - 20:30:28 MEST 

Hallihallo Rooters!


I have a TH2F h2D, I check a bin content a la
h2D->GetBinContent( h2D->FindBin(x,y)); //returns 17

I have a TF2 fitFcn,I check a value a la
fitFcn->Eval(x,y) // returns 12.5
//same with TF1::EvalPar(x,parameter)

Now I do
h2D->Add(fitFcn,-1.0);
h2D->GetBinContent( h2D->FindBin(x,y)); /returns 7.76

Naively I would expect 17-12.5 to be 4.5. Obviously I am too naive for
this problem.

I tried to use TH1F::Eval(TF1,"A"), which gave me (17+12.5=) 26.2,
which is at least consistent.

Sounds like TH2F::Add(TF1) uses another set of parameters. 


Any hint what I missunderstood?

Michael


PS: I am using  root 3.03/09  on RH Linux 7.2

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