{
"cells": [
{
"cell_type": "markdown",
"id": "53b1cdef",
"metadata": {},
"source": [
"# fit2d\n",
"Example illustrating how to fit a 2-d histogram of type y=f(x)\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Rene Brun \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:24 PM."
]
},
{
"cell_type": "markdown",
"id": "b76f3871",
"metadata": {},
"source": [
"generate a 2-d histogram using a TCutG"
]
},
{
"cell_type": "code",
"execution_count": 1,
"id": "213efeb1",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:24:44.082385Z",
"iopub.status.busy": "2026-05-19T20:24:44.082258Z",
"iopub.status.idle": "2026-05-19T20:24:44.432126Z",
"shell.execute_reply": "2026-05-19T20:24:44.431743Z"
}
},
"outputs": [],
"source": [
"const int n = 6;\n",
"float x[n] = {0.092,0.83,0.94,0.81,0.12,0.1};\n",
"float y[n] = {0.71,9.4,9,8,0.3,0.71};\n",
"TCutG *cut = new TCutG(\"cut\",n,x,y);\n",
"TH2F *h2 = new TH2F(\"h2\",\"h2\",40,0,1,40,0,10);\n",
"float u,v;\n",
"for (int i=0;i<100000;i++) {\n",
" u = gRandom->Rndm();\n",
" v = 10*gRandom->Rndm();\n",
" if (cut->IsInside(u,v)) h2->Fill(u,v);\n",
"}\n",
"TCanvas *c1 = new TCanvas(\"c1\",\"show profile\",600,900);\n",
"c1->Divide(1,2);\n",
"c1->cd(1);\n",
"h2->Draw();\n",
"c1->cd(2);"
]
},
{
"cell_type": "markdown",
"id": "dc65622d",
"metadata": {},
"source": [
"use a TProfile to convert the 2-d to 1-d problem"
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "04e519ce",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:24:44.434334Z",
"iopub.status.busy": "2026-05-19T20:24:44.434216Z",
"iopub.status.idle": "2026-05-19T20:24:44.665087Z",
"shell.execute_reply": "2026-05-19T20:24:44.664439Z"
}
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"****************************************\n",
"Minimizer is Linear / Migrad\n",
"Chi2 = 4501.58\n",
"NDf = 33\n",
"p0 = -0.47055 +/- 0.00713644 \n",
"p1 = 10.8033 +/- 0.0124078 \n"
]
}
],
"source": [
"TProfile *prof = h2->ProfileX();\n",
"prof->Fit(\"pol1\");"
]
},
{
"cell_type": "markdown",
"id": "a8b3d1c5",
"metadata": {},
"source": [
"Draw all canvases "
]
},
{
"cell_type": "code",
"execution_count": 3,
"id": "ae561303",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:24:44.666821Z",
"iopub.status.busy": "2026-05-19T20:24:44.666699Z",
"iopub.status.idle": "2026-05-19T20:24:44.903864Z",
"shell.execute_reply": "2026-05-19T20:24:44.903334Z"
}
},
"outputs": [
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"text/html": [
"\n",
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\n",
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""
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},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"%jsroot on\n",
"gROOT->GetListOfCanvases()->Draw()"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "ROOT C++",
"language": "c++",
"name": "root"
},
"language_info": {
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