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"# gr013_polar2\n",
"See the [TGraphPolar documentation](https://root.cern/doc/master/classTGraphPolar.html)\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",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:37 PM."
]
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"TCanvas * CPol = new TCanvas(\"CPol\",\"TGraphPolar Example\",500,500);\n",
"\n",
"Double_t theta[8];\n",
"Double_t radius[8];\n",
"Double_t etheta[8];\n",
"Double_t eradius[8];\n",
"\n",
"for (int i=0; i<8; i++) {\n",
" theta[i] = (i+1)*(TMath::Pi()/4.);\n",
" radius[i] = (i+1)*0.05;\n",
" etheta[i] = TMath::Pi()/8.;\n",
" eradius[i] = 0.05;\n",
"}\n",
"\n",
"TGraphPolar * grP1 = new TGraphPolar(8, theta, radius, etheta, eradius);\n",
"grP1->SetTitle(\"\");\n",
"\n",
"grP1->SetMarkerStyle(20);\n",
"grP1->SetMarkerSize(2.);\n",
"grP1->SetMarkerColor(4);\n",
"grP1->SetLineColor(2);\n",
"grP1->SetLineWidth(3);"
]
},
{
"cell_type": "markdown",
"id": "0a379abf",
"metadata": {},
"source": [
"Draw with polymarker and errors"
]
},
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"id": "90147df8",
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"source": [
"grP1->Draw(\"PE\");"
]
},
{
"cell_type": "markdown",
"id": "97264ac3",
"metadata": {},
"source": [
"To format the polar axis, we retrieve the TGraphPolargram.\n",
"First update the canvas, otherwise GetPolargram returns 0"
]
},
{
"cell_type": "code",
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"id": "d3bbe21c",
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"CPol->Update();\n",
"if (grP1->GetPolargram())\n",
" grP1->GetPolargram()->SetToRadian(); // tell ROOT that the theta values are in radians"
]
},
{
"cell_type": "markdown",
"id": "9dee35d7",
"metadata": {},
"source": [
"Draw all canvases "
]
},
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"source": [
"gROOT->GetListOfCanvases()->Draw()"
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}
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