Dear Rene' and Fons,
I am a ROOT user and I recently experienced the following problem concerning the treatment of errors.
I am fitting a set of data with asymmetric errors and retrieve the parameter errors calculated by MINOS.
I would expect that MINOS is also able to return an asymmetric error on the fitting parametres, but I do not manage to do that. I wonder if Minuit is able to treat the input asymmetric error distribution.
Here is the simple example of code I am using:
{
gStyle->SetOptFit();
gROOT->Reset();
c1 = new TCanvas("c1","A Simple Graph with error bars", 400, 800); c1->Divide(1, 3);
c1->cd(1);
c1_1->SetFillColor(42); c1_1->SetGrid(); c1_1->GetFrame()->SetFillColor(21); c1_1->GetFrame()->SetBorderSize(12);
Int_t n1 = 2;
Double_t x1 [n1] = {1, 2}; Double_t exl1[n1] = {0, 0}; Double_t exh1[n1] = {0, 0}; Double_t y1 [n1] = {4.1, 3.3};
gr1 = new TGraphAsymmErrors(n1, x1, y1, exl1, exh1, eyl1, eyh1);
gr1->SetTitle(0); gr1->SetMarkerColor(4); gr1->SetMarkerStyle(21); gr1->Draw("AP");
TF1 *f1 = new TF1("f1","[0]*exp(-[1]*x)", 1, 2);
f1->SetParameter(0, 1);
f1->SetParameter(1, 1);
//gr1->Fit(f1, "ve");
//gr1->Fit(f1, "vel");
gr1->Fit(f1, "vell");
//gr1->Fit("pol0", "ve");
}
Thanks,
Antonello Sbrizzi
-- Antonio Sbrizzi NIKHEF e-mail: asbrizzi_at_nikhef.nl P.O. Box 41882 phone: +31 20 5925115 Kruislaan 409 fax: +31 20 5925155 1098 SJ, Amsterdam handy1: +31 06 25503106 Nederland handy2: +39 333 6965997 http://www.nikhef.nl/~asbrizzi handy3: +49 0179 6569078Received on Mon Sep 11 2006 - 15:35:32 MEST
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