{
"cells": [
{
"cell_type": "markdown",
"id": "bf668ac3",
"metadata": {},
"source": [
"# pdf007_multivarGaus\n",
"Tutorial illustrating the multivariate gaussian random number generation\n",
"\n",
"\n",
"\n",
"\n",
"**Author:** Jorge Lopez \n",
"This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Tuesday, May 19, 2026 at 08:26 PM."
]
},
{
"cell_type": "code",
"execution_count": 1,
"id": "a35d0042",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:26:44.182722Z",
"iopub.status.busy": "2026-05-19T20:26:44.182589Z",
"iopub.status.idle": "2026-05-19T20:26:44.644556Z",
"shell.execute_reply": "2026-05-19T20:26:44.643917Z"
}
},
"outputs": [],
"source": [
"ROOT::Math::GSLRandomEngine rnd;\n",
"rnd.Initialize();\n",
"\n",
"const int dim = 3;\n",
"double pars[dim] = {0, 0, 0.5};\n",
"double genpars[dim] = {0, 0, 0};\n",
"double cov[dim * dim] = {1.0, -0.2, 0.0, -0.2, 1.0, 0.5, 0.0, 0.5, 0.75};\n",
"\n",
"TH1F* hX = new TH1F(\"hX\", \"hX;x;Counts\", 100, -5, 5);\n",
"TH1F* hY = new TH1F(\"hY\", \"hY;y;Counts\", 100, -5, 5);\n",
"TH1F* hZ = new TH1F(\"hZ\", \"hZ;z;Counts\", 100, -5, 5);\n",
"\n",
"TH2F* hXY = new TH2F(\"hXY\", \"hXY;x;y;Counts\", 100, -5, 5, 100, -5, 5);\n",
"TH2F* hXZ = new TH2F(\"hXZ\", \"hXZ;x;z;Counts\", 100, -5, 5, 100, -5, 5);\n",
"TH2F* hYZ = new TH2F(\"hYZ\", \"hYZ;y;z;Counts\", 100, -5, 5, 100, -5, 5);\n",
"\n",
"const int MAX = 10000;\n",
"for (int iEvent = 0; iEvent < MAX; ++iEvent) {\n",
" rnd.GaussianND(dim, pars, cov, genpars);\n",
" auto x = genpars[0];\n",
" auto y = genpars[1];\n",
" auto z = genpars[2];\n",
" hX->Fill(x);\n",
" hY->Fill(y);\n",
" hZ->Fill(z);\n",
" hXY->Fill(x, y);\n",
" hXZ->Fill(x, z);\n",
" hYZ->Fill(y, z);\n",
"}\n",
"\n",
"TCanvas* c = new TCanvas(\"c\", \"Multivariate gaussian random numbers\");\n",
"c->Divide(3, 2);\n",
"c->cd(1);\n",
"hX->Draw();\n",
"c->cd(2);\n",
"hY->Draw();\n",
"c->cd(3);\n",
"hZ->Draw();\n",
"c->cd(4);\n",
"hXY->Draw(\"COL\");\n",
"c->cd(5);\n",
"hXZ->Draw(\"COL\");\n",
"c->cd(6);\n",
"hYZ->Draw(\"COL\");"
]
},
{
"cell_type": "markdown",
"id": "515f0fd0",
"metadata": {},
"source": [
"Draw all canvases "
]
},
{
"cell_type": "code",
"execution_count": 2,
"id": "044f5d6d",
"metadata": {
"collapsed": false,
"execution": {
"iopub.execute_input": "2026-05-19T20:26:44.646406Z",
"iopub.status.busy": "2026-05-19T20:26:44.646273Z",
"iopub.status.idle": "2026-05-19T20:26:44.853433Z",
"shell.execute_reply": "2026-05-19T20:26:44.852754Z"
}
},
"outputs": [
{
"data": {
"text/html": [
"\n",
"\n",
"\n",
"
\n",
"\n",
"\n",
"\n"
],
"text/plain": [
""
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"gROOT->GetListOfCanvases()->Draw()"
]
}
],
"metadata": {
"kernelspec": {
"display_name": "ROOT C++",
"language": "c++",
"name": "root"
},
"language_info": {
"codemirror_mode": "text/x-c++src",
"file_extension": ".C",
"mimetype": " text/x-c++src",
"name": "c++"
}
},
"nbformat": 4,
"nbformat_minor": 5
}