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"source": [
"# hist007_TH1_liveupdate\n",
"Simple example illustrating how to use the C++ interpreter\n",
"to fill histograms in a loop and show the graphics results\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Rene Brun \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:11 PM."
]
},
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"source": [
"TCanvas *c1 = new TCanvas(\"c1\", \"Live update of histograms\", 200, 10, 600, 400);\n",
"c1->SetGrid();"
]
},
{
"cell_type": "markdown",
"id": "4e1bf110",
"metadata": {},
"source": [
"Create some histograms."
]
},
{
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"execution_count": 2,
"id": "275fa7b8",
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"execution": {
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"source": [
"auto *total = new TH1D(\"total\", \"This is the total distribution\", 100, -4, 4);\n",
"auto *main = new TH1D(\"main\", \"Main contributor\", 100, -4, 4);\n",
"auto *s1 = new TH1D(\"s1\", \"This is the first signal\", 100, -4, 4);\n",
"auto *s2 = new TH1D(\"s2\", \"This is the second signal\", 100, -4, 4);\n",
"total->Sumw2(); // store the sum of squares of weights"
]
},
{
"cell_type": "markdown",
"id": "2bf15e39",
"metadata": {},
"source": [
"set some style properties"
]
},
{
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"execution_count": 3,
"id": "6cb25673",
"metadata": {
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"execution": {
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"outputs": [],
"source": [
"total->SetMarkerStyle(21); // shape of the markers (\\see EMarkerStyle)\n",
"total->SetMarkerSize(0.7);\n",
"main->SetFillColor(16);\n",
"s1->SetFillColor(42);\n",
"s2->SetFillColor(46);\n",
"TSlider *slider = nullptr;"
]
},
{
"cell_type": "markdown",
"id": "ddc70a58",
"metadata": {},
"source": [
"Fill histograms randomly"
]
},
{
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"execution_count": 4,
"id": "aa165cd5",
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"data": {
"text/html": [
"\n",
"\n",
"\n",
"
\n",
"\n",
"\n",
"\n"
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"source": [
"TRandom3 rng;\n",
"const int kUPDATE = 500;\n",
"for (int i = 0; i < 10000; i++) {\n",
" float xmain = rng.Gaus(-1, 1.5);\n",
" float xs1 = rng.Gaus(-0.5, 0.5);\n",
" float xs2 = rng.Landau(1, 0.15);\n",
" main->Fill(xmain);\n",
" s1->Fill(xs1, 0.3);\n",
" s2->Fill(xs2, 0.2);\n",
" total->Fill(xmain);\n",
" total->Fill(xs1, 0.3);\n",
" total->Fill(xs2, 0.2);\n",
" if (i && (i % kUPDATE) == 0) {\n",
" if (i == kUPDATE) {\n",
" total->Draw(\"e1p\");\n",
" main->Draw(\"same\");\n",
" s1->Draw(\"same\");\n",
" s2->Draw(\"same\");\n",
" c1->Update();\n",
" slider = new TSlider(\"slider\", \"test\", 4.2, 0, 4.6, total->GetMaximum(), 38);\n",
" slider->SetFillColor(46);\n",
" }\n",
" if (slider)\n",
" slider->SetRange(0., 1. * i / 10000.);\n",
" c1->Modified();\n",
" c1->Update();\n",
" }\n",
"}\n",
"slider->SetRange(0., 1.);\n",
"c1->Modified();"
]
},
{
"cell_type": "markdown",
"id": "82add515",
"metadata": {},
"source": [
"Draw all canvases "
]
},
{
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"execution_count": 5,
"id": "25c7d651",
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],
"source": [
"%jsroot on\n",
"gROOT->GetListOfCanvases()->Draw()"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "ROOT C++",
"language": "c++",
"name": "root"
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