Hsum Timer

Demo of Timers.

Simple example illustrating how to use the C++ interpreter to fill histograms in a loop and show the graphics results This program is a variant of the tutorial "hsum". It illustrates the use of Timers.

Author: Rene Brun
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 24, 2022 at 03:56 PM.

In [1]:
Float_t progressRatio;
TSlider *slider;
TCanvas *c1;

A helper function is created:

In [2]:
%%cpp -d
void hsumUpdate()
{
// called when Timer times out
   if (slider) slider->SetRange(0, ::progressRatio);
   c1->Modified();
   c1->Update();
}

Arguments are defined.

In [3]:
Int_t nfill=100000;
In [4]:
c1 = new TCanvas("c1","The HSUM example",200,10,600,400);
c1->SetGrid();

Create some histograms.

In [5]:
auto total  = new TH1F("total","This is the total distribution",100,-4,4);
auto main   = new TH1F("main","Main contributor",100,-4,4);
auto s1     = new TH1F("s1","This is the first signal",100,-4,4);
auto s2     = new TH1F("s2","This is the second signal",100,-4,4);
total->Sumw2();   // store the sum of squares of weights
total->SetMarkerStyle(21);
total->SetMarkerSize(0.7);
main->SetFillColor(16);
s1->SetFillColor(42);
s2->SetFillColor(46);
total->SetMaximum(nfill/20.);
total->Draw("e1p");
main->Draw("same");
s1->Draw("same");
s2->Draw("same");
c1->Update();slider = new TSlider("slider",
   "test",4.2,0,4.6,0.8*total->GetMaximum(),38);
slider->SetFillColor(46);

Create a ttimer (hsumupdate called every 300 msec)

In [6]:
TTimer timer("hsumUpdate()",300);
timer.TurnOn();

Fill histograms randomly

In [7]:
Float_t xs1, xs2, xmain;
gRandom->SetSeed();
for (Int_t i=0; i<nfill; i++) {
   ::progressRatio = Float_t(i)/Float_t(nfill);
   if (gSystem->ProcessEvents()) break;
   xmain = gRandom->Gaus(-1,1.5);
   xs1   = gRandom->Gaus(-0.5,0.5);
   xs2   = gRandom->Landau(1,0.15);
   main->Fill(xmain);
   s1->Fill(xs1,0.3);
   s2->Fill(xs2,0.2);
   total->Fill(xmain);
   total->Fill(xs1,0.3);
   total->Fill(xs2,0.2);
}
timer.TurnOff();
hsumUpdate();

Draw all canvases

In [8]:
%jsroot on
gROOT->GetListOfCanvases()->Draw()