Copy TTree

ROOT
1

Hi,

I have a ntuple and I want to copy it with some cuts. The cut process is a little lengthy so I can not do simply CopyTree(selection). Here is my sample code where I want to take cut on x and y variables:

TChain *chain = new TChain("EVENT");
chain->Add("*.root");
int nEvent = chain->GetEntries();

TFile *file = new TFile("EventCut.root", "recreate");
TTree *newtree = chain->CloneTree(0);

Float_t x, y;
TBranch b_x, b_y;
chain->SetBranchAddress("x", &x, &b_x);
chain->SetBranchAddress("y", &y, &b_y);

for(int i=0; i<nEvent; i++){
    if(!cut(x, y)) continue;          // cut routine which return 1 if satisfied, otherwise 0
    newtree->Fill();
}

newtree->Write();
file->Close();

Now, my problem is the variables which I have accessed (here x and y) are not filled with actual values in the newtree. Either they are not filled or filled with some arbitrary values. Any idea will be appreciated.
Thanks.

2

Hi,

It may be a side-effect of the copy/paste but the code you have never reads the data from the input chain (i.e. it is missing a chain->GetEntry(i) );

Cheers,
Philippe.

3

Sorry, it is a typo. chain->GetEntry(i) is there.

4

Hi,

Then I don’t see any obvious problem. You could try to move the SetBranchAddress before the CloneTree. For further investigation, I would need a complete running example.

Cheers,
Philippe.