How to plot two graph in one canvas from two separate root file, the key of the graph is canvas

[pjana]

Hello,
I want to plot two graph from two separate root files into one canvas. I am able to get one plot but I could not able to plot two in one canvas. The key of the plot in the root file is canvas.
I have attached my code here.
I would be very grateful if anyone helps me.
Thanks!
first.root (11.7 KB)
second.root (11.7 KB)

void readplot(){
TFile* f1 = new TFile("first.root","READ");
TFile* f2 = new TFile("second.root","READ");
TCanvas* h1;
TCanvas* h2;
f1->GetObject("c",h1);
f2->GetObject("c",h2);
h1->Draw();
//h1->SetLineColor(kRed); 
//h2->SetLineColor(kBlue);
h2->Draw("same"); 
} 

[couet]

You access TCanvas. You cannot superimpose TCanavs like histograms.
Moreover your canvases do not contain histograms they contains TGraphAsymmErrors
You can try to get them from the canvas with:

TGraphAsymmErrors *g1 = (TGraphAsymmErrors*)c1->GetListOfPrimitives()->FindObject(.......);

[pjana]

Hello,
Many thanks!
Now I updated my code:

void Test()
{

TFile *f1 = TFile::Open("first.root");
TCanvas *c1 = (TCanvas*)f1->Get("c");
TGraphErrors *g1 = (TGraphErrors*)c1->GetPrimitive("Graph");
g1->GetYaxis()->SetRangeUser(-3,3);
g1->GetXaxis()->SetLimits(-0.5,0.5);
c1->Draw();
c1->SetGridy(0);
c1->SetGridx(0);

TFile *f2 = TFile::Open("second.root");
TCanvas *c2 = (TCanvas*)f2->Get("c");
TGraphErrors *g2 = (TGraphErrors*)c2->GetPrimitive("Graph");
g2->GetYaxis()->SetRangeUser(-3,3);
g2->GetXaxis()->SetLimits(-0.5,0.5);
c2->Draw();
c2->SetGridy(0);
c2->SetGridx(0);
}

Now I am getting error like

warning: null passed to a callee that requires a non-null argument [-Wnonnull]
g1->GetYaxis()->SetRangeUser(-3,3);

I am not sure what should I fill the rang. Could you please help me to fix this?

[couet]

You should not stored the canvases. You should store the TGraphs. Storing the canvases is not practical at all !
Any way with these two files you can do some tricks… but that’s really not straight forward:

void readplot(){
   TFile *f1 = TFile::Open("first.root");
   TCanvas *c1 = (TCanvas*)f1->Get("c");
   TPad *p1 = (TPad*)c1->GetPrimitive("p2");
   TGraphAsymmErrors *g1 = (TGraphAsymmErrors*)p1->GetPrimitive("2_Y_0190");

   TFile *f2 = TFile::Open("second.root");
   TCanvas *c2 = (TCanvas*)f2->Get("c");
   TPad *p2 = (TPad*)c2->GetPrimitive("p2");
   TGraphAsymmErrors *g2 = (TGraphAsymmErrors*)p2->GetPrimitive("2_Y_0190");

   auto C = new TCanvas();
   g1->Draw();
   g2->Draw("*");
}

[pjana]

Hello,
Using this script, I am not able to show the X axis range. Could you please give some suggestions that how can I show the X axis range also?

Lumi.C (1.4 KB)

[couet]

I cannot run your macro.

Processing Lumi.C...
Error in <TFile::TFile>: file /Users/couet/Downloads/2_Y_0190_PLT.root does not exist
Error in <HandleInterpreterException>: Trying to dereference null pointer or trying to call routine taking non-null arguments
Execution of your code was aborted.
In file included from input_line_9:1:
/Users/couet/Downloads/Lumi.C:4:28: warning: null passed to a callee that requires a non-null argument [-Wnonnull]
   TCanvas *c1 = (TCanvas*)f1->Get("c");
                           ^~

[pjana]

I ran using the below command.

root -l Lumi.C
It is producing the plots. I have attached
first.root (11.7 KB)
second.root (11.7 KB)
here the root file also.
2_Y_0190_BCM1FPCVD.root (11.7 KB)

[pjana]

Here is the updated script.
Lumi.C (1.3 KB)

[couet]

Still does not work:

root [0] 
Processing Lumi.C...
Error in <TFile::TFile>: file /Users/couet/Downloads/2_Y_0190_PLT.root does not exist
Error in <HandleInterpreterException>: Trying to dereference null pointer or trying to call routine taking non-null arguments
Execution of your code was aborted.
In file included from input_line_9:1:
/Users/couet/Downloads/Lumi.C:4:28: warning: null passed to a callee that requires a non-null argument [-Wnonnull]
   TCanvas *c1 = (TCanvas*)f1->Get("c");
                           ^~

[pjana]

Here is the updated script and root files
second.root (11.7 KB)
2_Y_0190_BCM1FPCVD.root (11.7 KB)
Lumi.C (1.3 KB)

first.root (11.7 KB)

It should work now.

Many Thanks!!

[couet]

void Lumi(){

   TFile *f1 = TFile::Open("first.root");
   TCanvas *c1 = (TCanvas*)f1->Get("c");
   TPad *p1 = (TPad*)c1->GetPrimitive("p2");
   TGraphAsymmErrors *g1 = (TGraphAsymmErrors*)p1->GetPrimitive("2_Y_0190");
   g1->SetMarkerStyle(kCircle);
   g1->SetTitle("Y Plane scan, BCID 190//2017 XeXe,5.44 TeV");
   g1->SetMarkerColor(kRed);

   TFile *f2 = TFile::Open("second.root");
   TCanvas *c2 = (TCanvas*)f2->Get("c");
   TPad *p2 = (TPad*)c2->GetPrimitive("p2");
   TGraphAsymmErrors *g2 = (TGraphAsymmErrors*)p2->GetPrimitive("2_Y_0190");
   g2->SetMarkerStyle(kOpenSquare);
   g2->SetTitle("CMS Preliminary");
   g2->SetMarkerColor(kBlue);

   TFile *f3 = TFile::Open("2_Y_0190_BCM1FPCVD.root");
   TCanvas *c3 = (TCanvas*)f3->Get("c");
   TPad *p3 = (TPad*)c3->GetPrimitive("p2");
   TGraphAsymmErrors *g3 = (TGraphAsymmErrors*)p3->GetPrimitive("2_Y_0190");
   g3->SetLineColor(2);
   g3->SetTitle("VdM Scan:Fill 6295");
   g3->SetMarkerStyle(kFullSquare);
   g3->SetMarkerColor(kGreen);

   auto C = new TCanvas();
   auto mg  = new TMultiGraph();
   mg->Add(g1);
   mg->Add(g2);
   mg->Add(g3);
   mg->Draw("AL*");
}

[pjana]

Thanks so much!!!

[couet]

You’re welcome. But it would be much better to store directly the TGraphs instead of the TCanvas and the TPad, The way you proceed is really not practical.

[pjana]

Sorry! I will keep in mind next time.
Thank you!