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"# df016_vecOps\n",
"Process collections in RDataFrame with the help of RVec.\n",
"\n",
"This tutorial shows the potential of the VecOps approach for treating collections\n",
"stored in datasets, a situation very common in HEP data analysis.\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Danilo Piparo (CERN) \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:09 PM."
]
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"source": [
"using namespace ROOT;"
]
},
{
"cell_type": "markdown",
"id": "5513441c",
"metadata": {},
"source": [
"We re-create a set of points in a square.\n",
"This is a technical detail, just to create a dataset to play with!"
]
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"id": "2547578f",
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"auto unifGen = [](double) { return gRandom->Uniform(-1.0, 1.0); };\n",
"auto vGen = [&](int len) {\n",
" RVecD v(len);\n",
" std::transform(v.begin(), v.end(), v.begin(), unifGen);\n",
" return v;\n",
"};\n",
"RDataFrame d(1024);\n",
"auto d0 = d.Define(\"len\", []() { return (int)gRandom->Uniform(0, 16); })\n",
" .Define(\"x\", vGen, {\"len\"})\n",
" .Define(\"y\", vGen, {\"len\"});"
]
},
{
"cell_type": "markdown",
"id": "15596183",
"metadata": {},
"source": [
"Now we have in our hands d, a RDataFrame with two columns, x and y, which\n",
"hold collections of coordinates. The sizes of these collections vary.\n",
"Let's now define radii from the x and y coordinates. We'll do it treating\n",
"the collections stored in the columns without looping on the individual elements."
]
},
{
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"execution_count": 3,
"id": "c355279a",
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"source": [
"auto d1 = d0.Define(\"r\", \"sqrt(x*x + y*y)\");"
]
},
{
"cell_type": "markdown",
"id": "a6f8491c",
"metadata": {},
"source": [
"Now we want to plot 2 quarters of a ring with radii .5 and 1.\n",
"Note how the cuts are performed on RVecs, comparing them with integers and\n",
"among themselves."
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "4386b24f",
"metadata": {
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"execution": {
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"outputs": [],
"source": [
"auto ring_h = d1.Define(\"rInFig\", \"r > .5 && r < 1 && x*y < 0\")\n",
" .Define(\"yFig\", \"y[rInFig]\")\n",
" .Define(\"xFig\", \"x[rInFig]\")\n",
" .Histo2D({\"fig\", \"Two quarters of a ring\", 64, -1.1, 1.1, 64, -1.1, 1.1}, \"xFig\", \"yFig\");\n",
"\n",
"auto cring = new TCanvas();\n",
"ring_h->DrawCopy(\"Colz\");\n",
"\n",
"return 0;"
]
},
{
"cell_type": "markdown",
"id": "931ff842",
"metadata": {},
"source": [
"Draw all canvases "
]
},
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"execution_count": 5,
"id": "9462e14a",
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