{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "87212da1",
   "metadata": {},
   "source": [
    "# hist002_TH1_fillrandom_userfunc\n",
    "Fill a 1D histogram from a user-defined parametric function.\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:** Rene Brun, Giacomo Parolini  \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 08:11 PM.</small></i>"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "86130fba",
   "metadata": {},
   "source": [
    "Create a user-defined formula.\n",
    "A function (any dimension) or a formula may reference an already defined formula"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "1666018a",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:43.598798Z",
     "iopub.status.busy": "2026-05-19T20:11:43.598674Z",
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     "shell.execute_reply": "2026-05-19T20:11:43.909237Z"
    }
   },
   "outputs": [],
   "source": [
    "TFormula form1(\"form1\", \"abs(sin(x)/x)\");"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a2eee917",
   "metadata": {},
   "source": [
    "Create a 1D function using the formula defined above and the predefined \"gaus\" formula."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "40d35619",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:43.911681Z",
     "iopub.status.busy": "2026-05-19T20:11:43.911520Z",
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     "shell.execute_reply": "2026-05-19T20:11:44.128872Z"
    }
   },
   "outputs": [],
   "source": [
    "double rangeMin = 0.0;\n",
    "double rangeMax = 10.0;\n",
    "TF1 sqroot(\"sqroot\", \"x*gaus(0) + [3]*form1\", rangeMin, rangeMax);\n",
    "sqroot.SetLineColor(4);\n",
    "sqroot.SetLineWidth(6);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "9cb8cc22",
   "metadata": {},
   "source": [
    "Set parameters to the functions \"gaus\" and \"form1\"."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "e3a3b7f5",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:44.142167Z",
     "iopub.status.busy": "2026-05-19T20:11:44.141990Z",
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     "shell.execute_reply": "2026-05-19T20:11:44.355405Z"
    }
   },
   "outputs": [],
   "source": [
    "double gausScale = 10.0;  // [0]\n",
    "double gausMean = 4.0;    // [1]\n",
    "double gausVar = 1.0;     // [2]\n",
    "double form1Scale = 20.0; // [3]\n",
    "sqroot.SetParameters(gausScale, gausMean, gausVar, form1Scale);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4ec18389",
   "metadata": {},
   "source": [
    "Create a one dimensional histogram and fill it following the distribution in function sqroot."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "b34d8fb7",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:44.361440Z",
     "iopub.status.busy": "2026-05-19T20:11:44.361313Z",
     "iopub.status.idle": "2026-05-19T20:11:44.564753Z",
     "shell.execute_reply": "2026-05-19T20:11:44.564382Z"
    }
   },
   "outputs": [],
   "source": [
    "int nBins = 200;\n",
    "TH1D h1d(\"h1d\", \"Test random numbers\", nBins, rangeMin, rangeMax);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "1be6b39d",
   "metadata": {},
   "source": [
    "Use our user-defined function to fill the histogram with random values sampled from it."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "92332ef7",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:44.572210Z",
     "iopub.status.busy": "2026-05-19T20:11:44.572084Z",
     "iopub.status.idle": "2026-05-19T20:11:44.784401Z",
     "shell.execute_reply": "2026-05-19T20:11:44.783592Z"
    }
   },
   "outputs": [],
   "source": [
    "h1d.FillRandom(\"sqroot\", 10000);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e357597e",
   "metadata": {},
   "source": [
    "Open a ROOT file and save the formula, function and histogram"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "408f7e7b",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:44.786516Z",
     "iopub.status.busy": "2026-05-19T20:11:44.786379Z",
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     "shell.execute_reply": "2026-05-19T20:11:45.119703Z"
    }
   },
   "outputs": [],
   "source": [
    "auto myFile = std::unique_ptr<TFile>(TFile::Open(\"fillrandom_userfunc.root\", \"RECREATE\"));\n",
    "myFile->WriteObject(&form1, form1.GetName());\n",
    "myFile->WriteObject(&sqroot, sqroot.GetName());\n",
    "myFile->WriteObject(&h1d, h1d.GetName());"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "04d4d7ff",
   "metadata": {},
   "source": [
    "Draw all canvases "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "17a3106e",
   "metadata": {
    "collapsed": false,
    "execution": {
     "iopub.execute_input": "2026-05-19T20:11:45.159034Z",
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     "shell.execute_reply": "2026-05-19T20:11:45.366782Z"
    }
   },
   "outputs": [],
   "source": [
    "gROOT->GetListOfCanvases()->Draw()"
   ]
  }
 ],
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