Rename, comment and modernise graph tutorials

tutorials/graphs/data_basic.txt

@@ -0,0 +1,20 @@
+-3.000000	-0.989992
+-2.684211	-0.897212
+-2.368421	-0.715699
+-2.052632	-0.463406
+-1.736842	-0.165284
+-1.421053	0.149185
+-1.105263	0.448899
+-0.789474	0.704219
+-0.473684	0.889894
+-0.157895	0.987561
+0.157895	0.987561
+0.473684	0.889894
+0.789474	0.704219
+1.105263	0.448899
+1.421053	0.149185
+1.736842	-0.165284
+2.052632	-0.463406
+2.368421	-0.715699
+2.684211	-0.897212
+3.000000	-0.989992

tutorials/graphs/gr001_basic.C

@@ -1,37 +1,77 @@
 /// \file
 /// \ingroup tutorial_graphs
 /// \notebook
-/// Draw a simple graph.
+///
+/// This tutorial demonstrates how to create simple graphs in ROOT. The example is divided into two sections:
+/// - The first section plots data generated from arrays.
+/// - The second section plots data read from a text file.
 ///
 /// \macro_image
 /// \macro_code
-///
+/// 
 /// \author Rene Brun
 
-void graph() {
-   TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);
+#include<fstream> //Include the library for reading the data file
+
+void gr001_basic() {
+   TCanvas *c1 = new TCanvas("c1","Two simple graphs",200,10,700,500);
+
+   c1->Divide(2,1); //Dividing the canvas in subpads for distinguishing the two examples, [See documentation](https://root.cern/doc/master/classTCanvas.html)
 
-   c1->SetGrid();
+   //FIRST EXAMPLE (Available data)
+   c1->cd(1);
 
-   const Int_t n = 20;
+   const Int_t n = 20; //Fill the arrays x and y with the data points
    Double_t x[n], y[n];
    for (Int_t i=0;i<n;i++) {
      x[i] = i*0.1;
      y[i] = 10*sin(x[i]+0.2);
      printf(" i %i %f %f \n",i,x[i],y[i]);
    }
-   TGraph *gr = new TGraph(n,x,y);
-   gr->SetLineColor(2);
-   gr->SetLineWidth(4);
-   gr->SetMarkerColor(4);
-   gr->SetMarkerStyle(21);
-   gr->SetTitle("a simple graph");
-   gr->GetXaxis()->SetTitle("X title");
-   gr->GetYaxis()->SetTitle("Y title");
-   gr->Draw("ACP");
-
-   // TCanvas::Update() draws the frame, after which one can change it
-   c1->Update();
-   c1->GetFrame()->SetBorderSize(12);
-   c1->Modified();
+
+   TGraph *gr1 = new TGraph(n,x,y); //Create a TGraph object, storing the number of data n and the x, y variables
+
+   //Set the color, width and style for the markers and line
+   gr1->SetLineColor(2);
+   gr1->SetLineWidth(4);
+   gr1->SetMarkerColor(4);
+   gr1->SetMarkerStyle(21);
+   gr1->SetTitle("Graph from available data"); //Choose title for the graph
+   gr1->GetXaxis()->SetTitle("X title"); //Choose title for the axis
+   gr1->GetYaxis()->SetTitle("Y title");
+
+   //Uncomment the following line to set a custom range for the x-axis (respectivly for the y-axis):
+   //gr1->GetXaxis()->SetRangeUser(0, 1.8); 
+
+   gr1->Draw("ACP"); //"A" draw axes, "C" = draw a smooth line through the markers (optional) and "P" = draw markers for data points 
+   //Optional customization can be done on a ROOT interactive session
+
+
+   //SECOND EXAMPLE (Data stored in a text file)
+   c1->cd(2);
+
+   const Int_t m = 20; //Known number of data points in the file
+   Double_t w[m], z[m];
+
+   std::ifstream file("data_basic.txt"); // Open the data file
+
+   // Use a for loop to read the data
+   for (Int_t i = 0; i < m; i++) {
+       file >> w[i] >> z[i]; //Fill the arrays with the data from the file
+   }
+   file.close(); //Close the file after reading
+
+
+   TGraph *gr2 = new TGraph(m, w, z); //Create a TGraph object for the file data
+   gr2->SetLineColor(4);
+   gr2->SetLineWidth(2);
+   gr2->SetMarkerColor(2);
+   gr2->SetMarkerStyle(20);
+   gr2->SetTitle("Graph from data file");
+   gr2->GetXaxis()->SetTitle("W title");
+   gr2->GetYaxis()->SetTitle("Z title");
+
+
+   gr2->Draw("ACP");
 }
+

tutorials/graphs/gr004_err_asym.C

@@ -1,56 +1,31 @@
 /// \file
 /// \ingroup tutorial_graphs
 /// \notebook
-/// A macro to demonstrate the functionality of TGraph::Apply() method.
-/// TGraph::Apply applies a function `f` to all the data TGraph points.
-/// `f` may be a 1-D function TF1 or 2-d function TF2.
-/// The Y values of the graph are replaced by the new values computed using
-/// the function.
+///
+/// This tutorial demonstrates the use of TGraphAsymmErrors to plot a graph with asymmetrical errors on both the x and y axes.
+/// The errors for the x values are divided into low (left side of the marker) and high (right side of the marker) errors.
+/// Similarly, for the y values, there are low (lower side of the marker) and high (upper side of the marker) errors.
 ///
 /// \macro_image
 /// \macro_code
-///
+/// 
 /// \author Miro Helbich
 
-void graphApply()
-{
+void gr004_err_asym() {
+   TCanvas *c2 = new TCanvas("c2","", 700, 500);
+
+   c2->SetGrid();
    const Int_t npoints=3;
    Double_t xaxis[npoints] = {1.,2.,3.};
    Double_t yaxis[npoints] = {10.,20.,30.};
-   Double_t errorx[npoints] = {0.5,0.5,0.5};
-   Double_t errory[npoints] = {5.,5.,5.};
-
-   Double_t exl[npoints] = {0.5,0.5,0.5};
-   Double_t exh[npoints] = {0.5,0.5,0.5};
-   Double_t eyl[npoints] = {5.,5.,5.};
-   Double_t eyh[npoints] = {5.,5.,5.};
-
-   TGraph *gr1 = new TGraph(npoints,xaxis,yaxis);
-   TGraphErrors *gr2 = new TGraphErrors(npoints,xaxis,yaxis,errorx,errory);
-   TGraphAsymmErrors *gr3 = new TGraphAsymmErrors(npoints,xaxis,yaxis,exl,exh,eyl,eyh);
-   TF2 *ff = new TF2("ff","-1./y");
-
-   TCanvas *c1 = new TCanvas("c1","c1");
-   c1->Divide(2,3);
 
-   // TGraph
-   c1->cd(1);
-   gr1->DrawClone("A*");
-   c1->cd(2);
-   gr1->Apply(ff);
-   gr1->Draw("A*");
+   Double_t exl[npoints] = {0.5,0.2,0.1}; //Lower x errors
+   Double_t exh[npoints] = {0.5,0.3,0.4}; //Higher x errors
+   Double_t eyl[npoints] = {3.,5.,4.}; //Lower y errors
+   Double_t eyh[npoints] = {3.,5.,4.}; //Higher y errors
 
-   // TGraphErrors
-   c1->cd(3);
-   gr2->DrawClone("A*");
-   c1->cd(4);
-   gr2->Apply(ff);
-   gr2->Draw("A*");
+   TGraphAsymmErrors *gr = new TGraphAsymmErrors(npoints,xaxis,yaxis,exl,exh,eyl,eyh); //Create the TGraphAsymmErrors object with data and asymmetrical errors
 
-   // TGraphAsymmErrors
-   c1->cd(5);
-   gr3->DrawClone("A*");
-   c1->cd(6);
-   gr3->Apply(ff);
-   gr3->Draw("A*");
+   gr->SetTitle("A simple graph with asymmetrical errors");
+   gr->Draw("A*"); //"A" = draw axes and "*" = draw markers at the points with error bars
 }

tutorials/graphs/gr005_apply.C

@@ -2,55 +2,34 @@
 /// \ingroup tutorial_graphs
 /// \notebook
 /// A macro to demonstrate the functionality of TGraph::Apply() method.
-/// TGraph::Apply applies a function `f` to all the data TGraph points.
-/// `f` may be a 1-D function TF1 or 2-d function TF2.
-/// The Y values of the graph are replaced by the new values computed using
-/// the function.
+/// TGraph::Apply applies a function `f` to all the data TGraph points, `f` may be a 1-D function TF1 or 2-d function TF2.
+/// The Y values of the graph are replaced by the new values computed using the function.
+///
+///
+/// The Apply() method can be used as well for TGraphErrors and TGraphAsymmErrors.
 ///
 /// \macro_image
 /// \macro_code
 ///
 /// \author Miro Helbich
 
-void graphApply()
-{
+void gr005_apply() {
+
    const Int_t npoints=3;
    Double_t xaxis[npoints] = {1.,2.,3.};
    Double_t yaxis[npoints] = {10.,20.,30.};
-   Double_t errorx[npoints] = {0.5,0.5,0.5};
-   Double_t errory[npoints] = {5.,5.,5.};
-
-   Double_t exl[npoints] = {0.5,0.5,0.5};
-   Double_t exh[npoints] = {0.5,0.5,0.5};
-   Double_t eyl[npoints] = {5.,5.,5.};
-   Double_t eyh[npoints] = {5.,5.,5.};
 
    TGraph *gr1 = new TGraph(npoints,xaxis,yaxis);
-   TGraphErrors *gr2 = new TGraphErrors(npoints,xaxis,yaxis,errorx,errory);
-   TGraphAsymmErrors *gr3 = new TGraphAsymmErrors(npoints,xaxis,yaxis,exl,exh,eyl,eyh);
-   TF2 *ff = new TF2("ff","-1./y");
+   TF2 *ff = new TF2("ff","-1./y"); //Defining the function `f`
 
-   TCanvas *c1 = new TCanvas("c1","c1");
-   c1->Divide(2,3);
+   TCanvas *c1 = new TCanvas("c1","c1", 0,0,700,500);
+   c1->Divide(2,1);
 
-   // TGraph
    c1->cd(1);
-   gr1->DrawClone("A*");
+   gr1->DrawClone("A*"); //Using DrawClone to create a copy of the graph in the canvas.
    c1->cd(2);
-   gr1->Apply(ff);
-   gr1->Draw("A*");
-
-   // TGraphErrors
-   c1->cd(3);
-   gr2->DrawClone("A*");
-   c1->cd(4);
-   gr2->Apply(ff);
-   gr2->Draw("A*");
-
-   // TGraphAsymmErrors
-   c1->cd(5);
-   gr3->DrawClone("A*");
-   c1->cd(6);
-   gr3->Apply(ff);
-   gr3->Draw("A*");
+   gr1->Apply(ff); //Applies the function `f` to all the data TGraph points
+   gr1->Draw("A*"); 
+   /* Without DrawClone, the modifications to gr1 via Apply(ff) are reflected in the original graph
+   displayed in c1 (the two drawn graphs are not independent). */
 }

tutorials/graphs/gr007_multigraph.C

@@ -1,24 +1,26 @@
 /// \file
 /// \ingroup tutorial_graphs
 /// \notebook
-/// Create and Draw a TMultiGraph.
+/// TMultiGraph is used to combine multiple graphs into one plot. 
+/// Allowing to overlay different graphs can be useful for comparing different datasets
+/// or for plotting multiple related graphs on the same canvas.
 ///
 /// \macro_image
 /// \macro_code
 ///
 /// \author Rene Brun
 
 
-void multigraph()
-{
+void gr007_multigraph() {
    gStyle->SetOptFit();
    auto c1 = new TCanvas("c1","multigraph",700,500);
    c1->SetGrid();
 
-   // draw a frame to define the range
+   //Initialize a TMultiGraph to hold multiple graphs
+   //This ensures the entire dataset from all added graphs is visible without manual range adjustments.
    auto mg = new TMultiGraph();
 
-   // create first graph
+   //Create first graph
    const Int_t n1 = 10;
    Double_t px1[] = {-0.1, 0.05, 0.25, 0.35, 0.5, 0.61,0.7,0.85,0.89,0.95};
    Double_t py1[] = {-1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1};
@@ -31,10 +33,11 @@ void multigraph()
    gr1->Fit("gaus","q");
    auto func1 = (TF1 *) gr1->GetListOfFunctions()->FindObject("gaus");
    func1->SetLineColor(kBlue);
-
+
+   //Add the first graph to the multigraph
    mg->Add(gr1);
 
-   // create second graph
+   //Create second graph
    const Int_t n2 = 10;
    Float_t x2[]  = {-0.28, 0.005, 0.19, 0.29, 0.45, 0.56,0.65,0.80,0.90,1.01};
    Float_t y2[]  = {2.1,3.86,7,9,10,10.55,9.64,7.26,5.42,2};
@@ -47,13 +50,14 @@ void multigraph()
    gr2->Fit("pol5","q");
    auto func2 = (TF1 *) gr2->GetListOfFunctions()->FindObject("pol5");
    func2->SetLineColor(kRed);
-   func2->SetLineStyle(kDashed);
+   func2->SetLineStyle(2);
 
+   //Add the second graph to the multigraph
    mg->Add(gr2);
 
    mg->Draw("ap");
 
-   //force drawing of canvas to generate the fit TPaveStats
+   //Force drawing of canvas to generate the fit TPaveStats
    c1->Update();
 
    auto stats1 = (TPaveStats*) gr1->GetListOfFunctions()->FindObject("stats");

tutorials/graphs/gr008_multierrors.C

@@ -1,40 +1,44 @@
 /// \file
 /// \ingroup tutorial_graphs
 /// \notebook -js
-/// Draw a graph with multiple y errors
+/// Draw a graph with multiple errors. Multi errors can be usefull for distinguishing different type of errors,
+/// for example statistical and systematic errors.
 ///
 /// \macro_image
 /// \macro_code
-///
+/// 
 /// \author Simon Spies
 
-void gmultierrors() {
+void gr008_multierrors() {
    TCanvas *c1 = new TCanvas("c1", "A Simple Graph with multiple y-errors", 200, 10, 700, 500);
    c1->SetGrid();
    c1->GetFrame()->SetBorderSize(12);
 
    const Int_t np = 5;
    Double_t x[np]       = {0, 1, 2, 3, 4};
    Double_t y[np]       = {0, 2, 4, 1, 3};
-   Double_t exl[np]     = {0.3, 0.3, 0.3, 0.3, 0.3};
-   Double_t exh[np]     = {0.3, 0.3, 0.3, 0.3, 0.3};
-   Double_t eylstat[np] = {1, 0.5, 1, 0.5, 1};
-   Double_t eyhstat[np] = {0.5, 1, 0.5, 1, 0.5};
-   Double_t eylsys[np]  = {0.5, 0.4, 0.8, 0.3, 1.2};
-   Double_t eyhsys[np]  = {0.6, 0.7, 0.6, 0.4, 0.8};
+   Double_t exl[np]     = {0.3, 0.3, 0.3, 0.3, 0.3}; //Lower x errors
+   Double_t exh[np]     = {0.3, 0.3, 0.3, 0.3, 0.3}; //Higher x errors
+   Double_t eylstat[np] = {1, 0.5, 1, 0.5, 1}; //Lower y statistical errors
+   Double_t eyhstat[np] = {0.5, 1, 0.5, 1, 0.5}; //Higher y statistical errors
+   Double_t eylsys[np]  = {0.5, 0.4, 0.8, 0.3, 1.2}; //Lower y systematic errors
+   Double_t eyhsys[np]  = {0.6, 0.7, 0.6, 0.4, 0.8}; //Higher y systematic errors
 
-   TGraphMultiErrors* gme = new TGraphMultiErrors("gme", "TGraphMultiErrors Example", np, x, y, exl, exh, eylstat, eyhstat);
-   gme->AddYError(np, eylsys, eyhsys);
+   TGraphMultiErrors *gme = new TGraphMultiErrors("gme", "TGraphMultiErrors Example", np, x, y, exl, exh, eylstat, eyhstat); //Create the TGraphMultiErrors object
+   gme->AddYError(np, eylsys, eyhsys); //Add the systematic y-errors to the graph
    gme->SetMarkerStyle(20);
    gme->SetLineColor(kRed);
-   gme->GetAttLine(0)->SetLineColor(kRed);
-   gme->GetAttLine(1)->SetLineColor(kBlue);
+   gme->GetAttLine(0)->SetLineColor(kRed); //Color for statistical error bars
+   gme->GetAttLine(1)->SetLineColor(kBlue); //Color for systematic error bars
    gme->GetAttFill(1)->SetFillStyle(0);
 
-   // Graph and x erros drawn with "APS"
-   // Stat Errors drawn with "Z"
-   // Sys Errors drawn with "5 s=0.5"
+   //Graph is drawn with the option "APS": "A" draw axes, "P" draw points and "S" draw symmetric horizontal error bars (x-errors)
+   //Statistical y-errors are drawn with the option "Z" vertical error bars.
+   //Systematic y-errors are drawn with the option "5 s=0.5":
+   //"5" draw rectangles to represent the systematic y-error bars.
+   //"s=0.5" scale the rectangles horizontally (along the x-axis) by a factor of 0.5.
    gme->Draw("APS ; Z ; 5 s=0.5");
 
+
    c1->Update();
 }