# graphpolar¶

Create and draw a polar graph.

Author: Olivier Couet
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, November 29, 2022 at 11:17 AM.

Illustrates how to use TGraphPolar

In [1]:
TCanvas * CPol = new TCanvas("CPol","TGraphPolar Examples",1200,600);
CPol->Divide(2,1);
CPol->cd(1);

Double_t xmin=0;
Double_t xmax=TMath::Pi()*2;

Double_t x[1000];
Double_t y[1000];
Double_t xval1[20];
Double_t yval1[20];

TF1 * fplot = new TF1("fplot","cos(2*x)*cos(20*x)",xmin,xmax);

for (Int_t ipt = 0; ipt < 1000; ipt++){
x[ipt] = ipt*(xmax-xmin)/1000+xmin;
y[ipt] = fplot->Eval(x[ipt]);
}

TGraphPolar * grP = new TGraphPolar(1000,x,y);
grP->SetLineColor(2);
grP->SetLineWidth(2);
grP->SetFillStyle(3012);
grP->SetFillColor(2);
grP->Draw("AFL");

for (Int_t ipt = 0; ipt < 20; ipt++){
xval1[ipt] = x[1000/20*ipt];
yval1[ipt] = y[1000/20*ipt];
}

TGraphPolar * grP1 = new TGraphPolar(20,xval1,yval1);
grP1->SetMarkerStyle(29);
grP1->SetMarkerSize(2);
grP1->SetMarkerColor(4);
grP1->SetLineColor(4);
grP1->Draw("CP");


Update, otherwise GetPolargram returns 0

In [2]:
CPol->Update();
if (grP1->GetPolargram()) {
grP1->GetPolargram()->SetTextColor(8);
grP1->GetPolargram()->SetRangePolar(-TMath::Pi(),TMath::Pi());
grP1->GetPolargram()->SetNdivPolar(703);
}

CPol->cd(2);
Double_t x2[30];
Double_t y2[30];
Double_t ex[30];
Double_t ey[30];
for (Int_t ipt = 0; ipt < 30; ipt++){
x2[ipt] = x[1000/30*ipt];
y2[ipt] = 1.2 + 0.4*sin(TMath::Pi()*2*ipt/30);
ex[ipt] = 0.2+0.1*cos(2*TMath::Pi()/30*ipt);
ey[ipt] = 0.2;
}

TGraphPolar * grPE = new TGraphPolar(30,x2,y2,ex,ey);
grPE->SetMarkerStyle(22);
grPE->SetMarkerSize(1.5);
grPE->SetMarkerColor(5);
grPE->SetLineColor(6);
grPE->SetLineWidth(2);
grPE->Draw("EP");


Update, otherwise GetPolargram returns 0

In [3]:
CPol->Update();

if (grPE->GetPolargram()) {
grPE->GetPolargram()->SetTextSize(0.03);
grPE->GetPolargram()->SetTwoPi();

gROOT->GetListOfCanvases()->Draw()