Hi Martin,
I am not sure I properly understood your situation but it seems that
you are trying to
- open a file
- create some histo
- close the file
- open another file
- create some more histo and maybe add to the first histos.
- close the other file
- display all the histo.
If this is the case, what you want to do is call
TH1::AddDirectory(kFALSE);
This tells the system to NOT add the histogram to the current file.
The default is to attach any new histogram to the current file and the
consequence is that when the current file is close, ALL its attached
histograms are deleted. When you use hwhatever->SetDirectory(0) you
are explicitly de-attaching the histogram from which ever file it could
have been attached to. TH1::AddDirectory makes this unattached behavior
the default.
Cheers,
Philippe.
-----Original Message-----
From: owner-roottalk@pcroot.cern.ch
[mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Martin Turner
Sent: Tuesday, April 09, 2002 5:00 AM
To: roottalk@pcroot.cern.ch
Subject: [ROOT] problems with using more than 1 branch.
Hello ROOT experts,
This is the frame of some code I have:
TFile *f =new TFile("Lambda_analysis.root","READ");
TTree *lambda_tree =(TTree*)f.Get("Lambda_analysis");
//Do analysis
f->close()
TFile *f =new TFile("Lambda_analysis.root","READ");
TTree *lambda_tree =(TTree*)f.Get("Lambda_analysis_track");
//ie. a different branch
TH1F* hpt_all_pion=new TH1F("pion pt","pion pt",100,0,10);
lambda_tree2->Draw("ftrack_pt>> pion pt");
This prints nothing except the Canvas and Pad.
It will work if I use hwhatever->SetDirectory(0), but I must do this for
every histogram. Clearly this is messy. Is there any way I can specify
where to place or subsequent histograms. It seems to get confused by using
another branch before it. What exactly is happening?
Martin
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