Adding a circle on a contour plot

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1

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_ROOT Version:_6.22/00
Platform: Ubuntu 20.04.1 LTS (WSL2)
Compiler: GNU or GCC

Hello,
I have created a contour plot of the magnetic flux density of an octupole magnet. Now I want to add/draw a circle on the contour plot with the radius r = 0.045 at the center. How do I do that?

#include "TFile.h"
#include "TTree.h"
#include "TCanvas.h"
#include "TH1F.h"
#include <iostream>

using namespace std;


  void Contour_Plot(){
   const Int_t NCont = 50;
   gStyle->SetNumberContours(NCont);
   auto g = new TGraph2D("Contour_data.txt","%lg %lg %lg");
   g->SetNpx(200);
   g->SetNpy(200);
   g->SetTitle("Contour plot of the magnetic flux density (T) in the x-y plane");
   g->GetHistogram()->GetXaxis()->SetTitle("x (m)");
   g->GetHistogram()->GetYaxis()->SetTitle("y (m)");
   g->SetLineWidth(1);
   g->SetLineStyle(1);
   g->Draw("colz cont6 ");
   
  TCanvas *c = new TCanvas("c", "c");
  g->Draw("COLZ");
  g->GetHistogram()->GetYaxis()->SetRangeUser(-0.07, 0.07);
  g->GetHistogram()->GetXaxis()->SetRangeUser(-0.07, 0.07);
  c->SetRealAspectRatio();
  c->Modified(); c->Update();
   
}
2

Try:

TEllipse *e = new TEllipse(0., 0., 0.045); e->SetFillStyle(0); e->Draw();
gPad->Modified(); gPad->Update();
3

Thanks for the help. Do you know how I can enlarge my contour plot?

4

Can you provide Contour_data.txt so we can see what to enlarge ?

5

Maybe: TCanvas *c = new TCanvas("c", "c", 1000, 1000);

6

I solved it by including more data into my contour plot.