Single TTree from TChain

[Demosthene]

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ROOT Version: 6.14.04
Platform: SLC6
Compiler: gcc62

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Hi, I’d like to be able to manipulate a number of root files (with similar contents) as one, for the purposes of projecting trees into various histograms and “befriending” with other trees etc.

For instance, if I do

>>> from ROOT import *
>>> chain = TChain("nominal")
>>> chain.Add("*.root")
15
>>> chain.GetEntries()
1220986L
>>> chain.GetTree().GetEntries()
6330L

It seems TChain::GetTree() returns a pointer to the last tree only. How can I get a single tree, containing the contents of all the root files in my TChain, in a similar way to hadding those files?

Thanks!

[Demosthene]

Actually never mind, should have read the docs better

[pcanal]

@Demosthene

I’d like to be able to manipulate a number of root files (with similar contents) as one, for the purposes of projecting trees into various histograms and “befriending” with other trees etc.

This is explicitly the purpose of TChain … [alternatively you can merge the files into one very large one in several including using the hadd command line tool]

Cheers,
Philippe.