How to correctly draw a TH2 Polar plot

ROOT
1

Hi!

I’m trying to produce a TH2 polar plot:

void test () {

	gStyle->SetOptStat(0);
	Double_t theta[] = {30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360};
	double r = 0.06;

	TCanvas* c = new TCanvas("c", "c", 800, 800);

	TH2D* d = new TH2D("d", "", 2, -1, 1, 2, -1, 1);
	TH2D* h = new TH2D("p", "", 12, 0, 360, 12, 0, 1);
	
	d->GetXaxis()->SetLabelSize(0);
	d->GetYaxis()->SetLabelSize(0);
	
	for (double t : theta) {
		h->Fill(t, r);
		r += 0.06;
	}
	
	d->Draw("COL");
	h->Draw("col pol same");
}

The output:

unnamed
unnamed.png798×774 11.9 KB

I digged a bit in the forum here and I couldn’t find a way to avoid a dummy TH2 in order to draw the polar plot correctly. Is it mandatory?
Above all, why do I get a doily instead of the funny iridescent circle I want?

PS:
Sorry for bothering over and over, almost every single day.

2

I must admit I do not really understand the result you get … May be using the POL option on Lego would be better ?

{
   gStyle->SetOptStat(0);
   Double_t theta[] = {30, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360};
   double r = 0.06;

   TCanvas* c = new TCanvas("c", "c", 800, 800);
   c->SetTheta(90);
   c->SetPhi(0.);

   TH2D* h = new TH2D("p", "", 12, 0, 360, 12, 0, 1);

   for (double t : theta) {
      h->Fill(t, r);
      r += 0.06;
   }

   h->Draw("lego2 pol");
}

06
Screenshot 2019-03-14 at 14.35.06.jpg1566×1464 318 KB

3

That’s much better.
Is it possible to get circular sectors instead of triangles?

4

This is because you have a few bins only… with more bins it will be more circular.

5

Uhm…
Optical effects then. :thinking:

One last thing: how to rotate the circle by 90 deg clockwise?

6 
   c->SetPhi(270.);
7

Thank you, couet. :slight_smile: