{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "8d403bd0",
   "metadata": {},
   "source": [
    "# df008_createDataSetFromScratch\n",
    "Create data from scratch with RDataFrame.\n",
    "\n",
    "This tutorial shows how to create a dataset from scratch with RDataFrame\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Danilo Piparo (CERN)  \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 08:09 PM.</small></i>"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "984c6eaf",
   "metadata": {},
   "source": [
    "We create an empty data frame of 100 entries"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "fd4136c9",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:09:35.133380Z",
     "iopub.status.busy": "2026-05-19T20:09:35.133235Z",
     "iopub.status.idle": "2026-05-19T20:09:35.475145Z",
     "shell.execute_reply": "2026-05-19T20:09:35.469388Z"
    }
   },
   "outputs": [],
   "source": [
    "ROOT::RDataFrame df(100);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "01bc4981",
   "metadata": {},
   "source": [
    "We now fill it with random numbers"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "8217da44",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:09:35.492400Z",
     "iopub.status.busy": "2026-05-19T20:09:35.492257Z",
     "iopub.status.idle": "2026-05-19T20:09:35.967645Z",
     "shell.execute_reply": "2026-05-19T20:09:35.967043Z"
    }
   },
   "outputs": [],
   "source": [
    "gRandom->SetSeed(1);\n",
    "auto df_1 = df.Define(\"rnd\", []() { return gRandom->Gaus(); });"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "cfbd99a7",
   "metadata": {},
   "source": [
    "And we write out the dataset on disk"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "46ad2f08",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:09:35.969448Z",
     "iopub.status.busy": "2026-05-19T20:09:35.969322Z",
     "iopub.status.idle": "2026-05-19T20:09:37.110737Z",
     "shell.execute_reply": "2026-05-19T20:09:37.110120Z"
    }
   },
   "outputs": [],
   "source": [
    "df_1.Snapshot(\"randomNumbers\", \"df008_createDataSetFromScratch.root\");"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "ROOT C++",
   "language": "c++",
   "name": "root"
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   "codemirror_mode": "text/x-c++src",
   "file_extension": ".C",
   "mimetype": " text/x-c++src",
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