Error in <TROOT::WriteTObject>: The current directory (Rint) is not associated with a file. The object (Graph) has not been written

[mendoza]

_ROOT Version: 6.22/02
Platform: Ubuntu 20.04
_Compiler: gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0

Dear developers,

I am having some trouble to write a TGraph object into a root file. I obtain the following error:

[mendoza]

Error in TROOT::WriteTObject: The current directory (Rint) is not associated with a file. The object (Graph) has not been written.

Please find attached the root macro I am using.

Thanks in advance!

Kind regards,

Diego
analyzer2.C (1.5 KB)

[jblomer]

Before calling grph->Write(), set the current directory to the output file with graphs->cd().

[mendoza]

Dear jblomer,

I have tried what you suggested and the error is still the same.

Best,

Diego

[couet]

I simplified your macro (because we do not have you data files) and applied @jblomer recommendation . The macro is now:

int analyzer2()
{
   int n = 51;
   int n2 = 11;
   TTree * TreeM;
   TBranch * Ener;
   string file_name1 = "ExN02_";
   string file_name2 = "keV.root";
   int energy = 500;
   TFile * graphs = new TFile("graphs.root", "RECREATE");

   for(int j = 0; j<n2; j++) {
      int energy2 = energy - 50;
      string prim_energy = to_string(energy);

      int kin_ener_Bfield;
      int energy_arr[n];
      int counts[n];

//       for(int i = 0; i<n; i++) {
//
//          string  ene = to_string(energy2);
//          string str = file_name1 + prim_energy + "_"+ ene + file_name2;
//          const char * file_name = str.c_str();
//
//          cout << file_name << endl;
//          TFile *file = TFile::Open(file_name, "READ");
//          TreeM = (TTree*)file->Get("TreeM");
//          counts[i] = TreeM->GetEntries("(sqrt((X-18)*(X-18)+Z*Z) < 0.4) && PID==11");
//          energy_arr[i] = energy2;
//          file->Close();
//
//          energy2 = energy2 + 2;
//       }

      TGraph *grph = new TGraph(n,energy_arr,counts);

      grph->GetYaxis()->SetTitle("Counts");
      grph->GetXaxis()->SetTitle("Kinetic Energy for B-field [keV]");
      grph->SetMarkerStyle(21);
      grph->SetMarkerColor(2);
      grph->SetMarkerSize(.5);
      graphs->cd();
      grph->Write();
      energy = energy + 10;

   }

   graphs->Close();

   return 0;
}

And the graphs are saved in the file:

% rootls  graphs.root
Graph  Graph  Graph  Graph  Graph  Graph  Graph  Graph  Graph  Graph  Graph

Well they all have the same name because you did not change it.

[mendoza]

Dear couet,

Thanks for the answer. You werre right, it works perfectly! It was me that was repeating a previous error.

Thanks all for the help.

Best,

Diego

[mendoza]

Actually, I would ask very quickly how can I change the name of these graphs when they are saved in the file.

Thanks,

Diego

[Axel]

@couet a TGraph isn’t a TNamed so there’s no way to customize its name I suppose?

[couet]

@mendoza

Actually, I would ask very quickly how can I change the name of these graphs when they are saved in the file.

Here is a new version of the reduced macro showing how to proceed.

int analyzer2()
{
   int n = 51;
   int n2 = 11;
   TTree * TreeM;
   TBranch * Ener;
   string file_name1 = "ExN02_";
   string file_name2 = "keV.root";
   int energy = 500;
   TFile * graphs = new TFile("graphs.root", "RECREATE");

   for(int j = 0; j<n2; j++) {
      int energy2 = energy - 50;
      string prim_energy = to_string(energy);

      int kin_ener_Bfield;
      int energy_arr[n];
      int counts[n];

      TGraph *grph = new TGraph(n,energy_arr,counts);
      grph->SetName(Form("Graph_number_%d",j));
      grph->SetTitle(Form("This is the Graph number %d",j));

      grph->GetYaxis()->SetTitle("Counts");
      grph->GetXaxis()->SetTitle("Kinetic Energy for B-field [keV]");
      grph->SetMarkerStyle(21);
      grph->SetMarkerColor(2);
      grph->SetMarkerSize(.5);
      graphs->cd();
      grph->Write();
      energy = energy + 10;

   }

   graphs->Close();

   return 0;
}

It gives:

$ root -l analyzer2.C  
root [0] 
Processing analyzer2.C...
(int) 0
root [1] .q
$ rootls -l graphs.root
TGraph  May 25 17:16 2021 Graph_number_0   "This is the Graph number 0"
TGraph  May 25 17:16 2021 Graph_number_1   "This is the Graph number 1"
TGraph  May 25 17:16 2021 Graph_number_10  "This is the Graph number 10"
TGraph  May 25 17:16 2021 Graph_number_2   "This is the Graph number 2"
TGraph  May 25 17:16 2021 Graph_number_3   "This is the Graph number 3"
TGraph  May 25 17:16 2021 Graph_number_4   "This is the Graph number 4"
TGraph  May 25 17:16 2021 Graph_number_5   "This is the Graph number 5"
TGraph  May 25 17:16 2021 Graph_number_6   "This is the Graph number 6"
TGraph  May 25 17:16 2021 Graph_number_7   "This is the Graph number 7"
TGraph  May 25 17:16 2021 Graph_number_8   "This is the Graph number 8"
TGraph  May 25 17:16 2021 Graph_number_9   "This is the Graph number 9"
$

[mendoza]

Thank you so much, it works very well!

Best,

Diego