TTree::Draw and size of vector

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[quote=“brun”]Hi Kaspi,
The doc of TTree::Draw says
Rene[/quote]
Sorry, I must have missed it. I apologize.

If I use the “@” convention, it works. But if use it without “@”:

chain.Draw("branchT2EV.TrkAx.size()", cut);

I get the following error message:

Warning in <TTreeFormula::DefinedVariable>: Can not call method on content of vector<double> in branchT2EV.TrkAx.size()
Error in <TTreeFormula::Compile>:  Part of the Variable "branchT2EV.TrkAx.size()" exists but some of it is not accessible or useable

Thanks again,

Kašpi.