tdf003_profiles.C File Reference

Detailed Description

This tutorial illustrates how to use TProfiles in combination with the TDataFrame.

See the documentation of TProfile and TProfile2D to better understand the analogy of this code with the example one.

#include "TFile.h"
#include "TH1F.h"
#include "TRandom.h"
#include "TTree.h"

#include "ROOT/TDataFrame.hxx"

// A simple helper function to fill a test tree: this makes the example
// stand-alone.
void fill_tree(const char *filename, const char *treeName)
{
   TFile f(filename, "RECREATE");
   TTree t(treeName, treeName);
   float px, py, pz;
   t.Branch("px", &px);
   t.Branch("py", &py);
   t.Branch("pz", &pz);
   for (int i = 0; i < 25000; i++) {
      gRandom->Rannor(px, py);
      pz = px * px + py * py;
      t.Fill();
   }
   t.Write();
   f.Close();
   return;
}

void tdf003_profiles()
{
   // We prepare an input tree to run on
   auto fileName = "tdf003_profiles.root";
   auto treeName = "myTree";
   fill_tree(fileName, treeName);

   // We read the tree from the file and create a TDataFrame.
   ROOT::Experimental::TDataFrame d(treeName, fileName, {"px", "py", "pz"});

   // Create the profiles
   auto hprof1d = d.Profile1D(TProfile("hprof1d", "Profile of pz versus px", 64, -4, 4));
   auto hprof2d = d.Profile2D(TProfile2D("hprof2d", "Profile of pz versus px and py", 40, -4, 4, 40, -4, 4, 0, 20));

   // And Draw
   auto c1 = new TCanvas("c1", "Profile histogram example", 200, 10, 700, 500);
   hprof1d->DrawClone();
   auto c2 = new TCanvas("c2", "Profile2D histogram example", 200, 10, 700, 500);
   c2->cd();
   hprof2d->DrawClone();
}

Date

February 2017

Author

Danilo Piparo

Definition in file tdf003_profiles.C.