Re: Remove entry from tree

see example in $ROOTSYS/tutorials/tree/copytree3.C

Rene Brun

Ida Häggström wrote:
> Dear Rooters,
>
> This is my first attempt to write a function for root, so please bear
> with me if this is actually really simple! =)
> I have a ROOT file containing some trees although I'm only interested
> in one of the trees (MyTree). This tree contains two branches (event1
> and event2) with like a million entries each that I want to use for
> some criteria. I want to either (Alt.1) remove some entries
> (according to the criteria) in that tree and save a new root file
> containing that tree, or (Alt.2) create a new tree with the same
> structure and save just the entries I'm interested in. Basically, in
> pseudo-code, this is what I want to do:
> -----------------------------
> |TFile* rootFile = new TFile("rootFile.root");
> TTree *MyTree; rootFile->GetObject("MyTree",MyTree);|
> Int_t nentries = (Int_t)(MyTree->GetEntries());
> MyTree->SetBranchAddress("event1",&event1);
> MyTree->SetBranchAddress("event2",&event2);
>
> for (Int_t i=0 ; i<nentries ; i++)
> if (event1 != event2)
> Alt1: remove this entry from the tree and save root-file
> Alt2: do nothing
> else
> Alt1: do nothing
> Alt2: save this entry to a new tree with same structure as
> MyTree, and save tree to a new root-file
> end
> ------------------------------------
> Can anyone lead me in the right direction? Thanks!
> Ida
>
Received on Wed May 19 2010 - 13:06:28 CEST