[Fwd: Re: TFile::Copy]
From: Rene Brun (Rene.Brun@cern.ch)
Date: Tue Feb 10 1998 - 10:42:45 MET
attached mail follows:
William J. Deninger wrote:
> Hello,
>
> I'm trying to figure out how to copy a TTree from one TFile to another.
> TFile::Copy doesn't seem to be implemented yet, and the following doesn't
> seem to work either:
>
> f1 = new TFile("f:/data/G2T076_076.root","update");
> f1.Delete("traceback;*"); // deleting old TTree object
>
> f2 = new TFile("f:/data/G2T076_076;1.root"); // file containing newest TTree
> object
> f1.cd();
> TTree *traceback = (TTree *) f2.Get("traceback"); // retrieve updated TTree
> object
> traceback.Write(); // write to f1
> f1.Write();
> f1.Close();
>
> Any suggestions?
In version 1.03/09 I introduced a function TTree::CloneTree
to do the job.
Example: assume an existing file with a Tree h1
and you want to copy this Tree to another file:
Root > TFile f1("oldfile.root");
Root > TTree *h1 = (TTree*)f1.Get("h1");
Root > TFile f2("newfile.root","recreate");
Root > TTree *h1new = h1->CloneTree(h1->GetEntries());
Root > h1new->Write();
Rene Brun
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