https://github.com/root-project/root
Tip revision: db2870b025dfc8a401f509206982871862975e29 authored by Unknown Author on 04 August 2006, 10:22:45 UTC
This commit was manufactured by cvs2svn to create tag 'v5-12-00b'.
This commit was manufactured by cvs2svn to create tag 'v5-12-00b'.
Tip revision: db2870b
fitcont.C
void fitcont()
{
// Example illustrating how to draw the n-sigma contour of a Minuit fit.
// To get the n-sigma contour the ERRDEF parameter in Minuit has to set
// to n^2. The fcn function has to be set before the routine is called.
//
// WARNING!!! This test works only with TMinuit
//
// The TGraph object is created via the interpreter. The user must cast it
// to a TGraph*
// Author; Rene Brun
TCanvas *c1 = new TCanvas("c1");
TH1F *h = new TH1F("h","My histogram",100,-3,3);
h->FillRandom("gaus",6000);
h->Fit("gaus");
c1->Update();
TCanvas *c2 = new TCanvas("c2","contours",10,10,600,800);
c2->Divide(1,2);
c2->cd(1);
//get first contour for parameter 1 versus parameter 2
TGraph *gr12 = (TGraph*)gMinuit->Contour(40,1,2);
gr12->Draw("alp");
c2->cd(2);
//Get contour for parameter 0 versus parameter 2 for ERRDEF=2
gMinuit->SetErrorDef(4); //note 4 and not 2!
TGraph *gr2 = (TGraph*)gMinuit->Contour(80,0,2);
gr2->SetFillColor(42);
gr2->Draw("alf");
//Get contour for parameter 0 versus parameter 2 for ERRDEF=1
gMinuit->SetErrorDef(1);
TGraph *gr1 = (TGraph*)gMinuit->Contour(80,0,2);
gr1->SetFillColor(38);
gr1->Draw("lf");
}