{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Building a Graph with Errors\n",
"
\n",
"\n",
"In this example we will build a graph with errors, display it and save it as an image."
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"First declare the values and the errors on the Y axis."
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"std::vector x_vals {1,2,3,4,5,6,7,8,9,10};\n",
"std::vector y_vals {6,12,14,20,22,24,35,45,44,53};\n",
"std::vector y_errs {5,5,4.7,4.5,4.2,5.1,2.9,4.1,4.8,5.43};\n",
"auto n_points = x_vals.size();"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Create the instance of the graph. The errors along the x axis are set to zero passing a *nullptr*."
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TGraphErrors graph(n_points, x_vals.data(), y_vals.data(), nullptr, y_errs.data());\n",
"graph.SetTitle(\"Measurement XYZ;lenght [cm];Arb.Units\");"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Make the plot look better."
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"graph.SetMarkerStyle(kOpenCircle);\n",
"graph.SetMarkerColor(kBlue);\n",
"graph.SetLineColor(kBlue);"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Create the canvas and draw the graph."
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TCanvas mycanvas;\n",
"graph.Draw(\"APE\");"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Define a linear function."
]
},
{
"cell_type": "code",
"execution_count": 5,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TF1 f(\"Linear law\", \"[0]+x*[1]\", .5, 10.5); "
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Let's make the funcion line nicer."
]
},
{
"cell_type": "code",
"execution_count": 6,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"f.SetLineColor(kRed);\n",
"f.SetLineStyle(2);"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Now fit the function to the graph and draw it."
]
},
{
"cell_type": "code",
"execution_count": 7,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
" FCN=3.84883 FROM MIGRAD STATUS=CONVERGED 31 CALLS 32 TOTAL\n",
" EDM=5.96982e-22 STRATEGY= 1 ERROR MATRIX ACCURATE \n",
" EXT PARAMETER STEP FIRST \n",
" NO. NAME VALUE ERROR SIZE DERIVATIVE \n",
" 1 p0 -1.01604e+00 3.33409e+00 1.48321e-03 -8.98235e-12\n",
" 2 p1 5.18756e+00 5.30717e-01 2.36095e-04 9.40487e-12\n"
]
}
],
"source": [
"graph.Fit(&f);\n",
"f.Draw(\"Same\");"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Build and draw a legend."
]
},
{
"cell_type": "code",
"execution_count": 8,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TLegend leg(.1, .7, .3, .9, \"Lab. Lesson 1\");\n",
"leg.SetFillColor(0);\n",
"graph.SetFillColor(0);\n",
"leg.AddEntry(&graph, \"Exp. Points\");\n",
"leg.AddEntry(&f, \"Th. Law\");\n",
"leg.Draw(\"Same\");"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Draw an arrow on the canvas."
]
},
{
"cell_type": "code",
"execution_count": 9,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TArrow arrow(8, 8, 6.2, 23, 0.02, \"|>\");\n",
"arrow.SetLineWidth(2);\n",
"arrow.Draw();"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Add some text to the plot."
]
},
{
"cell_type": "code",
"execution_count": 10,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"TLatex text(8.2, 7.5, \"#splitline{Maximum}{Deviation}\");\n",
"text.Draw();"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Display in the notebook what is in your canvas. Note how we first activate the interactive JavaScript visualisation."
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {
"collapsed": false
},
"outputs": [
{
"data": {
"text/html": [
"\n",
"\n",
"
\n",
"\n",
"\n"
],
"text/plain": [
""
]
},
"metadata": {},
"output_type": "display_data"
}
],
"source": [
"%jsroot on\n",
"mycanvas.Draw();"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"Save the content of your canvas to an image file on disk."
]
},
{
"cell_type": "code",
"execution_count": 12,
"metadata": {
"collapsed": false
},
"outputs": [
{
"name": "stderr",
"output_type": "stream",
"text": [
"Info in : pdf file graph_with_law.pdf has been created\n"
]
}
],
"source": [
"mycanvas.Print(\"graph_with_law.pdf\");"
]
}
],
"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": 0
}