fitExclude¶

Illustrates how to fit excluding points in a given range.

Author: Rene Brun
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, March 27, 2023 at 09:47 AM.

In [1]:

%%cpp -d
#include <TH1.h>
#include <TF1.h>
#include <TROOT.h>

bool reject;

Definition of a helper function:

In [2]:

%%cpp -d
double fline(double *x, double *par)
{
    if (reject && x[0] > 2.5 && x[0] < 3.5) {
      TF1::RejectPoint();
      return 0;
   }
   return par[0] + par[1]*x[0];
}

Create a source function

In [3]:

TF1 *f1 = new TF1("f1","[0] +[1]*x +gaus(2)",0,5);
f1->SetParameters(6,-1,5,3,0.2);

create and fill histogram according to the source function

In [4]:

TH1F *h = new TH1F("h","background + signal",100,0,5);
h->FillRandom("f1",2000);
TF1 *fl = new TF1("fl",fline,0,5,2);
fl->SetParameters(2,-1);

fit only the linear background excluding the signal area

In [5]:

reject = true;
h->Fit(fl,"0");
reject = false;

 FCN=84.1529 FROM MIGRAD    STATUS=CONVERGED      31 CALLS          32 TOTAL
                     EDM=4.69843e-21    STRATEGY= 1      ERROR MATRIX ACCURATE 
  EXT PARAMETER                                   STEP         FIRST   
  NO.   NAME      VALUE            ERROR          SIZE      DERIVATIVE 
   1  p0           2.84731e+01   9.46564e-01   1.81058e-03  -2.35464e-10
   2  p1          -4.81581e+00   2.65330e-01   5.07521e-04  -8.40016e-10

store 2 separate functions for visualization

In [6]:

TF1 *fleft = new TF1("fleft",fline,0,2.5,2);
fleft->SetParameters(fl->GetParameters());
h->GetListOfFunctions()->Add(fleft);
gROOT->GetListOfFunctions()->Remove(fleft);
TF1 *fright = new TF1("fright",fline,3.5,5,2);
fright->SetParameters(fl->GetParameters());
h->GetListOfFunctions()->Add(fright);
gROOT->GetListOfFunctions()->Remove(fright);
h->Draw();

Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1

Draw all canvases

In [7]:

%jsroot on
gROOT->GetListOfCanvases()->Draw()