Re: [ROOT] reading N-tuples

From: Rene Brun (Rene.Brun@cern.ch)
Date: Mon Feb 05 2001 - 17:13:20 MET


Hi Ilia,

Most of the time, one loops sequentially on the ntuple entries. However
a TNtuple, TTree allows direct access to any entry.
You can design an algorithm where you compute randomly the entry number to be
used or a set of random entries in your loop where you want to mix the entries.

Rene Brun

Ilia Ravinovich wrote:
> 
> Hi experts,
> 
> I have a created root N-tuple and and I have to calculate some variable
> using variables from mixed entries in the N-tuple. How I can do it in the
> following loop or using some different way ...
> 
>    Int_t nentries = (Int_t)ntuple_pair->GetEntries();
> 
>    cout << " Entries= " << nentries << endl;
> 
>    for (Int_t i=0;i<nentries;i++) {
>       ntuple_pair->GetEntry(i);
>    }
> 
> Thanks,
> 
> Ilia
> 
> ************************************************************************
> *                                                                      *
> *   Ilia Ravinovich                                                    *
> *   Department of Particle Physics             PPE Division            *
> *   Weizmann Institute of Science              Bld 892, 1D-015         *
> *   Rehovot 76100                              CERN, 1211 Geneva       *
> *   ISRAEL                                     Switzerland             *
> *                                                                      *
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