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"metadata": {},
"source": [
"# df010_trivialDataSource\n",
"Use the \"trivial data source\", an example data source implementation.\n",
"\n",
"This tutorial illustrates how use the RDataFrame in combination with a\n",
"RDataSource. In this case we use a RTrivialDS, which is nothing more\n",
"than a simple generator: it does not interface to any existing dataset.\n",
"The RTrivialDS has a single column, col0, which has value n for entry n.\n",
"The code for RTrivialDS is available at these links (header and source):\n",
"- https://github.com/root-project/root/blob/master/tree/dataframe/src/RTrivialDS.cxx\n",
"- https://github.com/root-project/root/blob/master/tree/dataframe/inc/ROOT/RTrivialDS.hxx\n",
"\n",
"Note that RTrivialDS is only a demo data source implementation and superior alternatives\n",
"typically exist for production use (e.g. constructing an empty RDataFrame as `RDataFrame(nEntries)`).\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."
]
},
{
"cell_type": "code",
"execution_count": 1,
"id": "f6447921",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:09:38.840088Z",
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"shell.execute_reply": "2026-05-19T20:09:39.283482Z"
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},
"outputs": [],
"source": [
"auto nEvents = 128U;\n",
"auto d_s = ROOT::RDF::MakeTrivialDataFrame(nEvents);"
]
},
{
"cell_type": "markdown",
"id": "d92edf35",
"metadata": {},
"source": [
"Now we have a regular RDataFrame: the ingestion of data is delegated to\n",
"the RDataSource. At this point everything works as before."
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "72ede287",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:09:39.296329Z",
"iopub.status.busy": "2026-05-19T20:09:39.296193Z",
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"shell.execute_reply": "2026-05-19T20:09:39.660630Z"
}
},
"outputs": [],
"source": [
"auto h_s = d_s.Define(\"x\", \"1./(1. + col0)\").Histo1D({\"h_s\", \"h_s\", 128, 0, .6}, \"x\");"
]
},
{
"cell_type": "markdown",
"id": "8c572baa",
"metadata": {},
"source": [
"Now we redo the same with a RDF from scratch and we draw the two histograms"
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "12a05bae",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:09:39.679365Z",
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"shell.execute_reply": "2026-05-19T20:09:39.881437Z"
}
},
"outputs": [],
"source": [
"ROOT::RDataFrame d(nEvents);"
]
},
{
"cell_type": "markdown",
"id": "2328a4f6",
"metadata": {},
"source": [
"This lambda redoes what the RTrivialDS provides"
]
},
{
"cell_type": "code",
"execution_count": 4,
"id": "38018211",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:09:39.885142Z",
"iopub.status.busy": "2026-05-19T20:09:39.885020Z",
"iopub.status.idle": "2026-05-19T20:09:41.319223Z",
"shell.execute_reply": "2026-05-19T20:09:41.318684Z"
}
},
"outputs": [],
"source": [
"auto g = []() {\n",
" static ULong64_t i = 0;\n",
" return i++;\n",
"};\n",
"auto h = d.Define(\"col0\", g).Define(\"x\", \"1./(1. + col0)\").Histo1D({\"h\", \"h\", 128, 0, .6}, \"x\");\n",
"\n",
"auto c_s = new TCanvas();\n",
"c_s->SetLogy();\n",
"h_s->DrawClone();\n",
"\n",
"auto c = new TCanvas();\n",
"c->SetLogy();\n",
"h->DrawClone();\n",
"\n",
"return 0;"
]
},
{
"cell_type": "markdown",
"id": "1b06c1e4",
"metadata": {},
"source": [
"Draw all canvases "
]
},
{
"cell_type": "code",
"execution_count": 5,
"id": "d7b488c5",
"metadata": {
"collapsed": false,
"execution": {
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"iopub.status.idle": "2026-05-19T20:09:41.537489Z",
"shell.execute_reply": "2026-05-19T20:09:41.536440Z"
}
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