Filling histograms from ntuples

From: Thomas Kraemerkaemper (kraemerk@Physik.Uni-Dortmund.DE)
Date: Thu Sep 04 1997 - 14:18:54 MEST


ROOTers,

I've some problem with filling predefined histograms from ntuples
(projecting ntuples into histograms):

my_ntuple->Draw("some_quantity >> my_histo", "some_selection")

seems to use ONLY selfdefined temporary histograms. When I tried to
instantiate the histogram before it is used in the command above,
nothing happens (I can't Draw() the histogram afterwards: canvas stays
empty). I would like to use predefined histograms to get a special
binning.

Also the command

my_ntuple->Project("my_histo", "some_quantity", "some_selection")

does not work in that way, albeit there is some indication from the
(at this point vague) documentation that it should.

And another question: Should Project() work like ntuple/project in
Paw, e.g. the projection is only _added_ to the histogram contents (no
reset)?

I've tried with 1.03/01 for AIX 4.1 and 1.02/00 for Solaris 2.4.


Tschuess, Thomas Kraemerkaemper.



This archive was generated by hypermail 2b29 : Tue Jan 04 2000 - 00:26:20 MET