The histogram cannot read rootfile to fillup. It is just empty

Newbie
, , ,
2

See the “analysis skeleton” generated by:

root -b -l -q Int_Run_020-020.root -e 'DataTree->MakeClass();'

BTW.

gROOT->cd(); // newly created histograms should go here
TH1F *histogram = new TH1F(...);