How to read trees that are inside TList within TDirectory using TChain?

[swati]

Dear all

I have to read TTrees from many root files together. The trees are located inside TLists within TDirectories. How does one read these trees using TChain? Whenever I use TChain to add the trees, root cannot find the tree.

The command I am trying to use is

TChain* ch = new TChain(“ResultsData/AnalysisMain_tree_FB768/fTreeEvent”)
ch->Add(“AnalysisResults1.root”)
ch->Add(“AnalysisResults2.root”)

I get the following error:

Error in TChain::LoadTree: Cannot find tree with name ResultsData/fTreeEvent in file datafile/AnalysisResults2.root

ROOT Version: 6.24/06
Platform: Ubuntu 20.04
Compiler: gcc

Thank you
Swati

[bellenot]

Welcome to the ROOT Forum!
As the message is telling, there is apparently no ResultsData/fTreeEvent tree in the datafile/AnalysisResults2.root file… Can you check with rootls -l datafile/AnalysisResults2.root?

[swati]

Hi Bellenot,

Thanks for the quick reply. I posted the error wrongly.
The error is

Error in TChain::LoadTree: Cannot find tree with name ResultsData/AnalysisMain_tree_FB768/fTreeEvent in file datafile/AnalysisResults1.root
Error in TChain::LoadTree: Cannot find tree with name ResultsData/AnalysisMain_tree_FB768/fTreeEvent in file datafile/AnalysisResults2.root

After running the makeclass command over a single root file, I run some codes and see the error.

Unfortunately, I cannot attach any files or pictures here as the website is not allowing to post them currently.

Thanks
Swati

[bellenot]

You should be able to attach files now

[swati]

Hi Bellenot,

After running the makeclass command over a single root file (test.C and test.h are generated), I run the following codes and see the error.

test.h (11.3 KB)
test.C (1.4 KB)
runChain.C (407 Bytes)

Here is the structure of the root file

Thanks
Swati

[bellenot]

OK, thanks for the example. Maybe @pcanal can tell if and how it’s supposed to work…

[pcanal]

@swati

The trees are located inside TLists

Out of curiosity why was this choice made (usually TTree are very large and thus there is only a few per files and TDirectory is already a list) …

? Whenever I use TChain to add the trees, root cannot find the tree.

This setup was not envisioned and is not supported in TChain.