df003_profiles.C File Reference

Detailed Description

Use TProfiles with RDataFrame.

This tutorial illustrates how to use TProfiles in combination with the RDataFrame. See the documentation of TProfile and TProfile2D to better understand the analogy of this code with the example one.

 
// A simple helper function to fill a test tree: this makes the example
// stand-alone.
void fill_tree(const char *treeName, const char *fileName)
{
   ROOT::RDataFrame d(25000);
   d.Define("px", []() { return gRandom->Gaus(); })
      .Define("py", []() { return gRandom->Gaus(); })
      .Define("pz", [](double px, double py) { return sqrt(px * px + py * py); }, {"px", "py"})
      .Snapshot(treeName, fileName);
}
 
void df003_profiles()
{
   // We prepare an input tree to run on
   auto fileName = "df003_profiles.root";
   auto treeName = "myTree";
   fill_tree(treeName, fileName);
 
   // We read the tree from the file and create a RDataFrame.
   ROOT::RDataFrame d(treeName, fileName, {"px", "py", "pz"});
 
   // Create the profiles
   auto hprof1d = d.Profile1D({"hprof1d", "Profile of py versus px", 64, -4, 4});
   auto hprof2d = d.Profile2D({"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);
   hprof2d->DrawClone("BOX");
}

Date

February 2017

Author

Danilo Piparo (CERN)

Definition in file df003_profiles.C.