[ROOT] recovering lost histograms

From: Ken Bloom (kenbloom@umich.edu)
Date: Wed Feb 27 2002 - 21:11:49 MET


Dear ROOT,

	I have two different ROOT ntuples, in two different files.  I use the 
MakeClass method to give me a skeleton of code that allows me to create and 
fill histograms based on the contents of the two ntuples, and I can use these 
classes like so:

	.L MyCodeA.C
	MyCodeA a;
	a.Loop();
	.L MyCodeB.C
	MyCodeB b;
	b.Loop();

By doing this, TFile objects are being created inside a and b, but I never get 
to see those.

	Now, I would like to compare the histograms made by a to those made by
b.  At this point, I believe I'm in a directory that belongs to b, so I can
see the histograms made by b, but seeing the ones made by a is harder.  I know
that I can see a list of those histograms via something like:

	TFile* f1 = 
(TFile*)gROOT->GetListOfFiles()->FindObject("/path/name/of/file");
	f1.Print();

but I seem to have trouble then grabbing the histograms in said list.

	So how can I get to use both sets of histograms simultaneously?  And 
is there a way to do this without going through gROOT?  I feel like I did 
things like this in PAW, and that it was much easier!  Thanks, best wishes.

						Ken

------------------------------------------------------------------------------
Ken Bloom, Karma Adjuster                                Department of Physics
734-763-2329 / 734-936-1817 (fax)                       University of Michigan
kenbloom@umich.edu                              http://www.umich.edu/~kenbloom



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