Finding the Tree name in a .root file

Newbie
,
1

I have recreated a .root file using TSelector and I want to use this file for further analysis e.g I subtracted some channel numbers in a histogram and made a new .root file where histograms are lying at shifted positions. Now while using this file into another root program (where I am generating more new histograms using the shifted one) it is giving me an error:

Error in <TChain::LoadTree>: Cannot find tree with name RoseNIAS in file RFshifted.root

I made this RFshifted.root file which has Tree Name RoseNIAS.

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ROOT Version: Not Provided
Platform: Not Provided
Compiler: Not Provided

2

Can you post here the output of:

$ root RFshifted.root
...
root [1] _file0->ls()

or the output of:

$ rootls -l RFshifted.root
3

image1.jpeg
image1.jpeg1365×712 154 KB

Dropping down to last entry:-

image2.jpeg
image2.jpeg1298×711 151 KB

4

So this file does not contain the TTree RoseNIAS … Indeed, it does not contain any TTree. It has only TH1D. So it is normal you get this message from TChain.

5

This is understandable. Tree is not forming but what is the way out in that case if I want to use this file further for analysis. Means after applying shifting to some of the histograms I saved it into a .root file. The header file is generated as:
** This class has been automatically generated by ROOT version 5.34/09 from TTree RoseNIAS/ROSE **

Now I want to use this file into another program where I am changing time-of-flight to energy (obviously with the corrected centroids) but while clubbing/chaining it is giving the error.

6

Your file does not contain a tree. It contains only histograms. You should create a tree (somehow) if you want to use a chain. That’s your data you should know what your tree should contain. Creating a tree from histograms is not the normal way. Usually you do the opposite.

7

Ok I have created a .root file having Tree with leaves and branches. But this I have created using

         TFile *f = new TFile("232Th_280MeV_2.001", "READ");
        TTree *RoseNIAS = (TTree* )f->Get("RoseNIAS");        
        Double_t ADC01_ADC[32];
        Double_t ADC02_ADC[32];
        Double_t TDC01_TDC[32];    //RoseNIAS is the name of tree
          
         RoseNIAS->SetBranchAddress("ADC01.ADC",ADC01_ADC);	
         RoseNIAS->SetBranchAddress("ADC02.ADC",ADC02_ADC);
         RoseNIAS->SetBranchAddress("TDC01.TDC",TDC01_TDC);

TFile *ff = new TFile("232Th_280MeV_2.root","RECREATE");
	TTree *FissionTree = new TTree("FissionTree", "having all the leaves");        

      UShort_t P8009,P8027,P8045,P8063,P8081,P8099,P8117,P8135,P8207,P8225;
      UShort_t E8009,E8027,E8045,E8063,E8081,E8099,E8117,E8135,E8207,E8225;
      UShort_t T8009,T8027,T8045,T8063,T8081,T8099,T8117,T8135,T8207,T8225;
      Long64_t i,j,entries;

	FissionTree->Branch("P8009",&P8009,"P8009/s");
	FissionTree->Branch("P8027",&P8027,"P8027/s");
	FissionTree->Branch("P8045",&P8045,"P8045/s");
	FissionTree->Branch("P8063",&P8063,"P8063/s");
        FissionTree->Branch("P8081",&P8081,"P8081/s");

so on… and then

for(i=0;i<entries;i++)
	{
	  RoseNIAS->GetEntry(i);
          if (!(i%50000)) printf("Percentage done=%.1f\n",100.0*i/entries);
     P8009=ADC01_ADC[0];  E8009=ADC01_ADC[1];    T8009=TDC01_TDC[0]; 
.
.
.
In the last
FissionTree->Fill();
	}

	ff->Write();
	ff->Close();

filling the tree and the writing.
I want to know is there any way in which I can use this tree to generate histograms further into a root file.
Also suppose I want to add some channels in timing “T8009”. How can I do that???

8

When you have a tree the Draw() method (for instance) creates histogram for you from the tree variables.
But may be you do not need tree at all ? I understood you already had the histograms.
What I was saying is that the method TChain::LoadTree needs a tree and you can not use it if you do not have a tree. Why do you need to use TChain ?

9

I need to use TChain in order to utilise the regenerated “.root” files (having histograms and some shifted peak histograms too) into a program where I need to obtain Energy expression from Time of flight and to apply some graphical cuts. Obviously I will club/add all the data files because all belong to same set of conditions. It is tedious to do things one by one with each file where I need to get the same kind of output everytime.

10

So:

auto h = new TH1D('h","h".....);
tree->Draw("v1>>h");

auto h = new TH1D('h","h".....);
tree->Draw("v1+v2>>h");
  • v1 and v2 are variables in your tree