{
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   "source": [
    "# tree101_basic\n",
    " Read data from an ascii file and create a root file with an histogram and an ntuple.\n",
    " See a variant of this macro in tree102_basic.C.\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Rene Brun  \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 08:17 PM.</small></i>"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "49d3341d",
   "metadata": {},
   "source": [
    "read file $ROOTSYS/tutorials/io/tree/basic.dat\n",
    "this file has 3 columns of float data"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "adaaa473",
   "metadata": {
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    "execution": {
     "iopub.execute_input": "2026-05-19T20:17:46.210442Z",
     "iopub.status.busy": "2026-05-19T20:17:46.210314Z",
     "iopub.status.idle": "2026-05-19T20:17:46.685455Z",
     "shell.execute_reply": "2026-05-19T20:17:46.685055Z"
    }
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "x = -1.102279, y = -1.799389, z = +4.452822\n",
      "x = +1.867178, y = -0.596622, z = +3.842313\n",
      "x = -0.524181, y = +1.868521, z = +3.766139\n",
      "x = -0.380611, y = +0.969128, z = +1.084074\n",
      "x = +0.552454, y = -0.212309, z = +0.350281\n",
      " found 1000 points\n"
     ]
    }
   ],
   "source": [
    "TString dir = gROOT->GetTutorialDir();\n",
    "dir.Append(\"/io/tree/\");\n",
    "dir.ReplaceAll(\"/./\", \"/\");\n",
    "ifstream in;\n",
    "in.open(TString::Format(\"%sbasic.dat\", dir.Data()));\n",
    "\n",
    "Float_t x, y, z;\n",
    "Int_t nlines = 0;\n",
    "auto f = TFile::Open(\"tree101.root\", \"RECREATE\");\n",
    "TH1F h1(\"h1\", \"x distribution\", 100, -4, 4);\n",
    "TNtuple ntuple(\"ntuple\",\"data from ascii file\", \"x:y:z\");\n",
    "\n",
    "while (1) {\n",
    "   in >> x >> y >> z;\n",
    "   if (!in.good())\n",
    "      break;\n",
    "   if (nlines < 5)\n",
    "      printf(\"x = %+8.6f, y = %+8.6f, z = %+8.6f\\n\", x, y, z);\n",
    "   h1.Fill(x);\n",
    "   ntuple.Fill(x, y, z);\n",
    "   nlines++;\n",
    "}\n",
    "printf(\" found %d points\\n\", nlines);\n",
    "in.close();\n",
    "f->Write();"
   ]
  }
 ],
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