Read the data in a TCanvas

ROOT
1

ROOT Version: Not Provided
_Platform: Centos 7
Compiler: Not Provided

Sys_Pt_IsoSFNom_All_IsoFCLoose.root (21.8 KB)

There are several OBJ in my root file, and I want to read the data in TGraphAsymmtry. This problem is quite similar with https://root-forum.cern.ch/t/convert-canvas-into-histogram-in-root/16322
However, I used the code in the answer like:

(1). TFile *th1 = new TFile("Sys_Pt_IsoSFNom_All_IsoFCLoose.root")
(2).TCanvas *c1 = (TCanvas*)t1->Get("Sys_ p_{T} [GeV]_IsoSFNom_All_IsoFCLoose")
(there is a star before c1 and after TCanvas. It disappeared after I post it)
(3).c1->ls()
Canvas Name=Sys_ p_{T} [GeV]_IsoSFNom_All_IsoFCLoose Title=Sys_ p_{T} [GeV]_IsoSFNom_All_IsoFCLoose Option=
 TCanvas fXlowNDC=0 fYlowNDC=0 fWNDC=1 fHNDC=1 Name= Sys_ p_{T} [GeV]_IsoSFNom_All_IsoFCLoose Title= Sys_ p_{T} [GeV]_IsoSFNom_All_IsoFCLoose Option=
  OBJ: TList	TList	Doubly linked list : 0
   TFrame  X1= 3.000000 Y1=0.001000 X2=500.000000 Y2=1000.000000
   OBJ: TH1F	Nom_ZmumuZmumuTPIsoIsoSFNomIsoFCLooseAllPtOCProbe	Z#rightarrow#mu#mu : 1 at: 0x3ba5ad0
   OBJ: TGraphAsymmErrors		Total : 1 at: 0x3be5010
   OBJ: TGraphAsymmErrors		isolBkg : 1 at: 0x3bebeb0
   OBJ: TGraphAsymmErrors		Statistics : 1 at: 0x3bec550
   OBJ: TGraphAsymmErrors		eta : 1 at: 0x3becbf0
   OBJ: TGraphAsymmErrors		mass : 1 at: 0x3bed290
   OBJ: TGraphAsymmErrors		Statistics (MC) : 1 at: 0x3bed930
   OBJ: TGraphAsymmErrors		tpdR : 1 at: 0x3bedfd0
   OBJ: TGraphAsymmErrors		probeQ : 1 at: 0x3bee670
   OBJ: TGraphAsymmErrors		tagIsol : 1 at: 0x3beed10
   OBJ: TGraphAsymmErrors		dRmuj : 1 at: 0x3bef3b0
   OBJ: TLegend	TPave  	X1= 40.746839 Y1=620.253547 X2=455.962026 Y2=835.443204
   Text  X=0.190000 Y=0.900000 Text=#font[72]{ATLAS} Internal
   Text  X=0.190000 Y=0.850000 Text=#sqrt{s} = 13 TeV, 44.3 fb^{-1}
   Text  X=0.920000 Y=0.900000 Text=IsoFCLoose
   Text  X=0.920000 Y=0.850000 Text=IsoSFNom
   Text  X=0.500000 Y=0.850000 Text=
(4). TH1F *th1 = (TH1F*)c1->GetPrimitive("Total")
(there is a star before th1 and after TH1F. It disappeared after I post it)

and also

TGraphAsymmErrors *tg1 = (TGraphAsymmErrors*)c1->GetPrimitive("Total")

doesn’t work
However, it said: nullptr.

Could you please help me?
I want to read the data in the TGraphAsymmtry objects.

2

All your graphs have nonempty titles (e.g. “Total”, “isolBkg”) but all names are empty (i.e. "", so that you cannot “find” them):

new TCanvas();
((TGraphAsymmErrors*)(c1->GetListOfPrimitives()->At(1)))->Draw("ALP");

BTW. When you post “source code” or “output” here, do remember to enclose them into two lines which contain just three characters ``` (see how your post has been edited above).

3

Many thanks Wile. It works well! And thanks for your instruction. This is my first time to post a question.
Cheers

4

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