gr014_polar3.C

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/// \file
/// \ingroup tutorial_graphs
/// \notebook
/// \preview Create a polar graph using a TF1 and draw it with PI axis.
/// See the [TGraphPolar documentation](https://root.cern/doc/master/classTGraphPolar.html)
///
/// Since TGraphPolar is a TGraphErrors, it is painted with
/// [TGraphPainter](https://root.cern/doc/master/classTGraphPainter.html) options.
///
/// \macro_image
/// \macro_code
/// \author Olivier Couet
 
void gr014_polar3()
{
   TCanvas *CPol = new TCanvas("CPol","TGraphPolar Examples",500,500);
 
   Double_t rmin = 0;
   Double_t rmax = TMath::Pi()*2;
   Double_t r[1000];
   Double_t theta[1000];
 
   TF1 *fp1 = new TF1("fplot","cos(x)",rmin,rmax);
   for (Int_t ipt = 0; ipt < 1000; ipt++) {
      r[ipt] = ipt*(rmax-rmin)/1000+rmin;
      theta[ipt] = fp1->Eval(r[ipt]);
   }
 
   TGraphPolar *grP1 = new TGraphPolar(1000, r, theta);
   grP1->SetTitle("");
   grP1->SetLineColor(2);
   grP1->Draw("AOL");
}