Re: [ROOT] Q: how to merge several trees into one and to write the result out?

From: Suzanne Panacek (spanacek@fnal.gov)
Date: Tue Jan 02 2001 - 20:34:18 MET 

Hi Pasha,
You can use the TChain::Merge method to a file from the collected trees.
Suzanne
----- Original Message -----
From: "Pasha Murat (630)840-8237@169G" <murat@ncdf41.fnal.gov>
To: "roottalk" <roottalk@pcroot.cern.ch>
Sent: Tuesday, January 02, 2001 12:51 PM
Subject: [ROOT] Q: how to merge several trees into one and to write the
result out?


> Dear Rooters,
>
> I'm pretty sure this little problem has already been solved. I'm trying to
merge
> several ROOT trees (all having the same structure) residing in different
files
> into a single one and to write the resulting tree out. The simpliest
procedure
> I tried - to create a chain and to write it out using methods of TChain
class
> doesn't do the job - I can create a chain
>
>   TChain c1("/STNTUPLE/h1");
>
>   c1.Add("/data/run1/einclusive/root/iceflt_ccj951.root");
>   c1.Add("/data/run1/einclusive/root/iceflt_ccj952.root");
>   c1.Add("/data/run1/einclusive/root/iceflt_ccj953.root");
>
> but I didn't find a way to either write the chain with all the events
out -
> TChain::Write doesn't seem to write out the events, or to copy contents
> of a chain into a new tree - smth. along these lines
>
> TFile output_file("output.root");
> TTree* output_tree = c1.CloneTree();
> output_file.Write();
>
> I'd appreciate any help here and I also think that that having a method
> TChain::CloneTree overloading TTree::CloneTree might be quite useful.
>
> Happy New Year and thanks, Pasha
>
>

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