Re: [ROOT] TTree event selection

From: Rene Brun (Rene.Brun@cern.ch)
Date: Tue Feb 24 2004 - 13:22:19 MET


Hi Mike,

To answer your question, I must know the relationship between
your variable "EventNum" and the TTree entry number
in your two Trees. Solutions to this kind of problem are typically
using TEventList or TTree::BuildIndex

Rene Brun

On Tue, 24 
Feb 2004, Mike Carson wrote:

> 
> Dear Rooters,
> 
> I've got two TTrees, tree1 and tree2, with the same variable list 
> (EventNum X Y Z). I'd like to select those events in tree2 which have the 
> same EventNum as the events in tree1. I can do this with a couple of for 
> loops but it takes too long. I also tried this:
> 
> Int_t numberOfEvents = tree1->GetEntries(); 
> Char_t myString[20];
> 
> for (Int_t i=0; i<numberOfEvents; i++) {
>  tree1->GetEvent(i);
>  sprintf(myString,"\"EventNum == %d \"",EventNum);
>  tree2->Draw(">>+eventList",myString);
> }
> 
> but that didn't work. I tried a similar thing with a TCut object instead 
> of myString...didn't work either. Any ideas?
> 
> I'm using root version 3.10/02, gcc 3.2.2, RH9.0. 
> 
> Many thanks,
> Mike.
> 



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