Day: September 14, 2016

ROOT has a built in C++ interpreter called Cling. One example of using Cling is:

% root
root [0] TF1 f1("f1", "sin(x)/x", -10.0, 10.0)
root [1] f1.Draw()

Note that the terminating “;” is not required at the end of each line.

Or you can write a ROOT macro, which is a collection of lines.

// file name = myprog1.C
void myprog1(){
   TCanvas *c1 = new TCanvas("c1" ,"Test" ,0 ,0 ,600 ,400) ;
   c1->SetGrid( ) ;
   TF1 *f1 = new TF1("f1", "sin(x)/x", -10.0, 10.0);
   f1->Draw();
   c1->Update();
}

You can execute your macros either by:

% root myprog1.C
// or
% root
root [0] .x myprog1.C

Your macros can also be compiled by adding some “dressing code”.

https://root.cern.ch/root/htmldoc/guides/primer/ROOTPrimer.html#interpretation-and-compilation

// file name = myprog2.C

//include some header files, not necessary for Cling.
#include "TApplication.h"
#include "TROOT.h"
#include "TCanvas.h"
#include "TF1.h"
using namespace std;

void myprog2() {
  TCanvas *c1 = new TCanvas("c1", "Test", 0, 0, 600, 400);
  c1->SetGrid();
  TF1 *f1 = new TF1("f1", "sin(x)/x", -10.0, 10.0);
  f1->Draw();
  c1->Update();
}

void StandaloneApplication(int argc, char** argv) {
  myprog2();
}

int main (int argc, char** argv) {
  TApplication app("ROOT Application", &argc, argv);
  StandaloneApplication(app.Argc(), app.Argv());
  app.Run();
  return 0;
}

% g++ -o myprog2 myprog2.C `root-config --cflags --libs`
./myprog2

Finally, you can use a set of bindings called PyROOTto interface to Python.

# file name = myprog3.py
from ROOT import TCanvas, TF1
c1=TCanvas("c1" ,"Test" ,0 ,0 ,600 ,400) 
c1.SetGrid ()
f1=TF1("f1", "sin(x)/x", -10.0, 10.0)
f1.Draw()
c1.Update()
raw_input('Press <ret> to end -> ')

% python myprog3.py