Hi Vitaliy,
Yes, this should be straightforward.
Follow the following steps;
1- connect the original file "first.root" with TTree T1
2- Set branch addresses for T1
3- Create new file "second.root"
4- Create new TTree T2
5- Create branches pointing to the old variables
6- Create new variables
7- Execute event loop
- for each entry T1->GetEntry(i);
- modify old variables in memory, compute new variable
- T2->Fill()
You can simplify steps 4 and 5 by using TTree::cloneTree or TTree::CopyTree.
See examples of use in $ROOTSYS/test/stress.cxx
See also examples in $ROOTSYS/tutorials/copytree.C and copytree2.C
Rene Brun
Vitaliy Ziskin wrote:
>
> Hello,
> Is there a way to take an ntuple and apply specific cuts on some entries
> and modify/calibrate other and print a set of midified collumns into a new
> ntuple. It sounds easy but (at least the way I see it) the ntuples are
> written row-wise and read collumn-wise.
>
> Thanks, Vitaliy
>
> =====================================================================
> Vitaliy Ziskin Tel: (617)253-7065
> MIT 26-547 http://www.lns.mit.edu/people/vziskin/
> 77 Massachusetts Ave
> Cambridge, Ma
> 02139
> ======================================================================
> "The memories of a man in his old age
> Are the deeds of a man in his prime"--Pink Floyd
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