Yes, you can get the contour for any user defined TF1. See the fitcont.C
example modified below
Rene Brun
double myfunc(double* x, double* par) {
return par[0]*TMath::Gaus(x[0],par[1],par[2]);
}
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);
TF1 *f1 = new TF1("f1",myfunc,-3,3,3);
f1->SetParameters(100.,0.,1.);
h->Fit(f1);
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");
}
Manuel Mussini wrote:
>
> Hi,
>
> I’m trying to plot a chi2 contour as described here:
>
> http://root.cern.ch/root/html/TMinuit.html#TMinuit:Contour
>
> the example fitcont.C works perfectly; is it possible to do the same
> thing using a user defined TF1 as fitting function?
>
> Is there an example to follow as tutorial?
>
> Thanks!
>
> Bye…
>
Received on Mon Mar 03 2008 - 22:11:58 CET
This archive was generated by hypermail 2.2.0 : Tue Mar 04 2008 - 11:50:01 CET