[ROOT] increment a specific element of a tree

From: payman hosseini (phossein@midway.uchicago.edu)
Date: Mon Dec 08 2003 - 23:29:46 MET 

hi
say i have a tree with these branches:
  TTree * t2 = new TTree("t2","raw correlations go here");
  t2->Branch("reference",&j,"reference/I");
  t2->Branch("target",&k,"target/I");
  t2->Branch("bin",&s,"bin/I");
  t2->Branch("value",&sum,"value/I");

and i fill it up like this:
  for (i=0;i<ntrials;i++)
    {
	......
	  for(k=j;k<n_units;k++)
	    {
		.......
	      for(s=-80;s<81;s++)
		{
		.........
		do calculations to find "sum"
		  t2->Fill();
		}
	    }
	}
    }


the reference(j), the target(k), and the bin(s) repeat periodically. "sum"
is always different.
after the first repetition of the reference, the target, and the bin, i do
not want to put them in the tree again. i only want to
increment the original value of "sum" in the tree. can this be done?


thank you very much,

paymon

i am using:
WindowsXP/NT/w2000 with VC++ 7.0, version 3.10/01 (good old tar
file) **WIN32GDK** 

thanks

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