How to access a histo from TDirectory root file?

General Chat
1

hi,
I have to draw histograms from a root file which has a lots of sub directory;
However, I have tried to write a macro to opne the file e draw the histogram like below;

TFile *f1=TFile::Open("DQM_V0001_R000000001__Global__CMSSW_X_Y_Z__RECO.root");

 TH1F *h1=(TH1F*)f1->Get("DQMData/Run/MuonGEMDigisV/Run summary/GEMDigisTask/CoPad/BunchCrossing/copad_bx_re-1_st1");//copad_bx_re-1_st1 is histo name

 TCanvas *c1=new TCanvas();
 c1->cd();
 h1->Draw("Histo");

I got a this error message below;
null passed to a callee that requires a non-null argument [-Wnonnull]
null passed to a callee that requires a non-null argument [-Wnonnull]
h1->Draw(“Histo”);
Mi Ran

rootfilefor validation
rootfilefor validation493×611 9.47 KB

What can I do to fix this problem?

2

After the Get is h1 is valid value or a nullptr?

3 
TH1F *h1=(TH1F*)f1->Get("DQMData/Run **1**/MuonGEMDigisV/Run summary/GEMDigisTask/CoPad/BunchCrossing/copad_bx_re-1_st1");

I have found my mistake that I missed run number in the path.
Thank you for your attention.