Re: h2root and histogramming

Axel Schwank (schwank@mail.desy.de)
Thu, 23 Jul 1998 10:26:55 +0200 (MET DST)

Dear Michal,
I'm not sure if I got all the points you had problems with, but I hope
this helps:
Regarding the converted NTuple, h2root converts the HBOOK NTuple into a
ROOT Tree of the same name, h9000 in your case. This Tree is divided into
several parts. (If one creates a Tree on his own, I assume this is
depending on the TTree.fAutoSave. Am I right ?)
See the directory of you file, which probably looks somehow like this:

TFile** make_cris_ntuple.root.0
TFile* make_cris_ntuple.root.0
KEY: TTree h9000;2 CRIS
KEY: TTree h9000;1 CRIS

In your macro, you only read the first part of the Tree:
TTree *t9000 = (TTree*)f1->Get("h9000;1");
Read the complete Tree by omitting the ";1".

Regarding your first question about filling the histograms, you are right
to use TH1::Fill (e.g. h2y->Fill(dy2)) to fill the histograms. I don't see
what's your problem here. But somewhere you need an event loop. Like this,
your histogram has only one entry (the first event).
Have a look at the Tutorials (Reading all/selected events of a ROOT Tree).

Regards,
Axel

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Axel Schwank

DESY H1-F22
Notkestrasse 85
D-22607 Hamburg

Rm. 1b/269
Tel (+49 40) 8998-3560
Fax (+49 40) 8998-4385

e-mail schwank@mail.desy.de
Quix 0165-6-2705109

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