{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "a03a511d",
   "metadata": {},
   "source": [
    "# gr012_polar\n",
    "\n",
    "Since TGraphPolar is a TGraphErrors, it is painted with\n",
    "[TGraphPainter](https://root.cern/doc/master/classTGraphPainter.html) options.\n",
    "\n",
    "With GetPolargram we retrieve the polar axis to format it; see the\n",
    "[TGraphPolargram documentation](https://root.cern/doc/master/classTGraphPolargram.html)\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Olivier Couet  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:37 PM.</small></i>"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "03893c4e",
   "metadata": {},
   "source": [
    "Illustrates how to use TGraphPolar"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2d391d10",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TCanvas * CPol = new TCanvas(\"CPol\",\"TGraphPolar Examples\",1200,600);\n",
    "CPol->Divide(2,1);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2dfd0062",
   "metadata": {},
   "source": [
    "Left-side pad. Two graphs without errors"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f71a019a",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "CPol->cd(1);\n",
    "Double_t xmin=0;\n",
    "Double_t xmax=TMath::Pi()*2;\n",
    "\n",
    "Double_t x[1000];\n",
    "Double_t y[1000];\n",
    "Double_t xval1[20];\n",
    "Double_t yval1[20];"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5227ee23",
   "metadata": {},
   "source": [
    "Graph 1 to be drawn with line and fill"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9d95f49f",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TF1 * fplot = new TF1(\"fplot\",\"cos(2*x)*cos(20*x)\",xmin,xmax);\n",
    "for (Int_t ipt = 0; ipt < 1000; ipt++){\n",
    "   x[ipt] = ipt*(xmax-xmin)/1000 + xmin;\n",
    "   y[ipt] = fplot->Eval(x[ipt]);\n",
    "}\n",
    "TGraphPolar * grP = new TGraphPolar(1000,x,y);\n",
    "grP->SetLineColor(2);\n",
    "grP->SetLineWidth(2);\n",
    "grP->SetFillStyle(3012);\n",
    "grP->SetFillColor(2);\n",
    "grP->Draw(\"AFL\");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "82a9d507",
   "metadata": {},
   "source": [
    "Graph 2 to be drawn superposed over graph 1, with curve and polymarker"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e87abaa2",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "for (Int_t ipt = 0; ipt < 20; ipt++){\n",
    "   xval1[ipt] = x[1000/20*ipt];\n",
    "   yval1[ipt] = y[1000/20*ipt];\n",
    "}\n",
    "TGraphPolar * grP1 = new TGraphPolar(20,xval1,yval1);\n",
    "grP1->SetMarkerStyle(29);\n",
    "grP1->SetMarkerSize(2);\n",
    "grP1->SetMarkerColor(4);\n",
    "grP1->SetLineColor(4);\n",
    "grP1->Draw(\"CP\");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3bc32ed5",
   "metadata": {},
   "source": [
    "To format the polar axis, we retrieve the TGraphPolargram.\n",
    "First update the canvas, otherwise GetPolargram returns 0"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f0282315",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "CPol->Update();\n",
    "if (grP1->GetPolargram()) {\n",
    "   grP1->GetPolargram()->SetTextColor(8);\n",
    "   grP1->GetPolargram()->SetRangePolar(-TMath::Pi(),TMath::Pi());\n",
    "   grP1->GetPolargram()->SetNdivPolar(703);\n",
    "   grP1->GetPolargram()->SetToRadian(); // tell ROOT that the x and xval1 are in radians\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "b9048ade",
   "metadata": {},
   "source": [
    "Right-side pad. One graph with errors"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "e4c4fc86",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "CPol->cd(2);\n",
    "Double_t x2[30];\n",
    "Double_t y2[30];\n",
    "Double_t ex[30];\n",
    "Double_t ey[30];\n",
    "for (Int_t ipt = 0; ipt < 30; ipt++){\n",
    "   x2[ipt] = x[1000/30*ipt];\n",
    "   y2[ipt] = 1.2 + 0.4*sin(TMath::Pi()*2*ipt/30);\n",
    "   ex[ipt] = 0.2+0.1*cos(2*TMath::Pi()/30*ipt);\n",
    "   ey[ipt] = 0.2;\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0e1522b5",
   "metadata": {},
   "source": [
    "Grah to be drawn with polymarker and errors"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "dce8a94e",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TGraphPolar * grPE = new TGraphPolar(30,x2,y2,ex,ey);\n",
    "grPE->SetMarkerStyle(22);\n",
    "grPE->SetMarkerSize(1.5);\n",
    "grPE->SetMarkerColor(5);\n",
    "grPE->SetLineColor(6);\n",
    "grPE->SetLineWidth(2);\n",
    "grPE->Draw(\"EP\");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "11056d07",
   "metadata": {},
   "source": [
    "To format the polar axis, we retrieve the TGraphPolargram.\n",
    "First update the canvas, otherwise GetPolargram returns 0"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "dad844e9",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "CPol->Update();\n",
    "if (grPE->GetPolargram()) {\n",
    "   grPE->GetPolargram()->SetTextSize(0.03);\n",
    "   grPE->GetPolargram()->SetTwoPi();\n",
    "   grPE->GetPolargram()->SetToRadian(); // tell ROOT that the x2 values are in radians\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "87fcd096",
   "metadata": {},
   "source": [
    "Draw all canvases "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "63847db4",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "gROOT->GetListOfCanvases()->Draw()"
   ]
  }
 ],
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