Looping over the Tree branches

Newbie
1

Hi,

I have a rootfile which has a tree and it has branches (energy, channel, board, energyshort, timestamp). I want to loop over all the channel and board number. How to do that. I have the macro which does for one channel and one board number.psdB0C6.C (752 Bytes)

Here is the root file.

2

You can try using TTree::GetListOfBranches() to loop over all branches in your file.

3

I don’t know for what reason the TTree::GetListOfBranches method would need to be used.

Here’s something that might really help:

{
  TFile *f = TFile::Open("compass_run_244.root");
  if ((!f) || f->IsZombie()) { delete f; return; } // just a precaution
  TTree *t; f->GetObject("Data", t);
  if (!t) { delete f; return; } // just a precaution
  gROOT->cd(); // newly created histograms will not be connected to "f"
  Int_t Board_min = Int_t(t->GetMinimum("Board") + 0.5);
  Int_t Board_max = Int_t(t->GetMaximum("Board") + 0.5);
  Int_t Channel_min = Int_t(t->GetMinimum("Channel") + 0.5);
  Int_t Channel_max = Int_t(t->GetMaximum("Channel") + 0.5);
#if 0 /* 0 or 1 */
  // each Board and Channel pair in a separate canvas
  for (Int_t i = Board_min; i <= Board_max; i++) {
    for (Int_t j = Channel_min; j <= Channel_max; j++) {
      TCanvas *c = new TCanvas(TString::Format("c_%d_%d", i, j),
                               TString::Format("Board %d Channel %d", i, j));
      t->Draw(TString::Format("(EnergyShort+rndm(1)-0.5)/(Energy+rndm(7)-0.5) : Energy+rndm(3)-0.5 >> hist_%d_%d(1500,0,1500,50,0.9,1.0)", i, j),
              TString::Format("Board==%d && Channel==%d && Energy>50", i, j),
              "colz");
      c->Modified(); c->Update(); // make sure it’s really (re)drawn
    }
  }
#else /* 0 or 1 */
  // each Board and Channel pair in a separate pad (all in one canvas)
  TCanvas *c = new TCanvas("c", "All boards and channels");
  c->DivideSquare((Board_max - Board_min + 1) * (Channel_max - Channel_min + 1));
  Int_t pad = 1;
  for (Int_t i = Board_min; i <= Board_max; i++) {
    for (Int_t j = Channel_min; j <= Channel_max; j++) {
      c->cd(pad++);
      t->Draw(TString::Format("(EnergyShort+rndm(1)-0.5)/(Energy+rndm(7)-0.5) : Energy+rndm(3)-0.5 >> hist_%d_%d(1500,0,1500,50,0.9,1.0)", i, j),
              TString::Format("Board==%d && Channel==%d && Energy>50", i, j),
              "colz");
      gPad->Modified(); gPad->Update(); // make sure it’s really (re)drawn
    }
  }
  c->cd(0);
  c->Modified(); c->Update(); // make sure it’s really (re)drawn
#endif /* 0 or 1 */
  delete f; // automatically deletes "t", too
}
1 Like
4

Thanks a lot for the help. Can I save all the histograms in a root file instead of projecting it on the terminal?

5

If you do not want to draw histograms, replace "colz" with "goff" (and do not create any canvases).

If you want to save all histograms in a ROOT file, replace gROOT->cd(); with:

TFile *fout = TFile::Open("output_file.root", "recreate");

and right before or after delete f; add:

if (fout) fout->Write();
delete fout; // automatically deletes all histograms, too
6

I tried this but the file is empty.
NO histograms are saved in the file.

7

It works now. Thanks

8

How t get the colored histograms? After saving it to file it is all black.

9

SomeHisto->Draw("colz"); // Draw Option: colz