Hi, The short answer is: check out the functionality of TDirectory::cd. More specifically, you probably want to something like: file1 = new TFile("mainhisto.root","RECREATE"); TH1F * h0 = new TH1F("h0",....); file2 = new TFile("secondary.root","RECREATE"); TH1F * h1 = new TH1F("h1",...); file1->cd(); TH1F * h2 = new TH1F("h2",...); In this example, h0 and h2 will be in the file mainhisto while h1 is in the file secondary. Also since I created the pointer variable h0,h1,h2 I can access the histograms until I actually close the file (independantly of which file was created last or cd'ed to). I suspect that you might also be relying on the facility of the ROOT command line that let it load/created the object automatically. This is not a good thing if you are inside a script and thus should strive to write your code as standard C++ (Using ACLiC to quickly check the syntax). Anyway, on the command line you can automatically retrieve/access object in the current ROOT directory. Use TDirectory::cd to force a specific directory as the current directory. For example: file1 = new TFile("mainhisto.root","READ"); ... here the object in mainhisto are available .... file2 = new TFile("secondary.root","READ"); ... here the object in secondary are available .... file1->cd() ... here the object in mainhisto are available .... Cheers, Philippe. -----Original Message----- From: owner-roottalk@pcroot.cern.ch [mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Ahmet Sedat Ayan Sent: Tuesday, January 15, 2002 10:17 AM To: roottalk@pcroot.cern.ch Subject: [ROOT] lost histos?? Hi All, my question is the following: I read an ntuple (root) file and create many histograms e.g. ........ OBJ: TH1F h0 L> 3.5 : 0 OBJ: TH1F h1 L> 4. : 0 OBJ: TH1F h2 L> 5. : 0 etc.. ...... I would like to write two of these historgrams in different files (one histogram in one file). But when I create a file, say f1.root, to write h1 , I can not access the other histos anymore. I understand that when I create the f1.root , current directory becomes this file but i do not know how to go back to the directory in which I couls list and see all other histograms, objects etc as shown above... I would appreciate any comments and helps... Thanks, Ahmet ROOT versions: 3.01/06 on SunSparc *************** Ahmet Sedat Ayan Physics & Astronomy Dept. Van Allen Hall University of Iowa Iowa City, IA, 52242 Voice : (++ 1 319) 335-1941 (W) (GMT-6) Occupation : Ph.D Candidate (But still dreamer!) e-mail : ayan@cms.physics.uiowa.edu web : http://jazz.physics.uiowa.edu/~ayan
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