// a macro to draw a set of Beta distributions

{

  gROOT->Reset();

// first make a canvas and a 2D histogram for the axes

  TCanvas* c1 = new TCanvas("c1", "c1", 10, 10, 500, 500);
  c1->SetBottomMargin(0.15);
  c1->SetLeftMargin(0.15);

// create functions to be plotted

  TF1* f1 = new TF1("f1","TMath::BetaDist(x,[0],[1])", 0, 1);
  f1->SetParameter(0, 2.);
  f1->SetParameter(1, 3.);

  TF1* f2 = new TF1("f2","TMath::BetaDist(x,[0],[1])", 0, 1);
  f2->SetParameter(0, 5.);
  f2->SetParameter(1, 2);

  TF1* f3 = new TF1("f3","TMath::BetaDist(x,[0],[1])", 0, 1);
  f3->SetParameter(0, 2.);
  f3->SetParameter(1, 2.);

// use f1 to set axis properties

  f1->SetMinimum(0);                   // y axis min and max
  f1->SetMaximum(3.0);
  f1->SetRange(0., 1.0);               // x axis

  gStyle->SetOptStat(0);               // turn off statistics box
  f1->SetTitle("");                    // turn off global title
  f1->GetHistogram()->GetYaxis()->SetTitle("f(x;#alpha,#beta)");
  f1->GetHistogram()->GetXaxis()->SetTitle("x");

  gStyle->SetOptLogy(0);                    // 1 for log scale

// See TStyle for how to change attributes

  f1->GetXaxis()->SetTitleOffset(1.2); // factor multiplies default offset
  f1->GetYaxis()->SetTitleOffset(1.5);

  f1->GetXaxis()->SetTitleSize(0.04); // default = 0.04 (??? in manual, 0.02)
  f1->GetYaxis()->SetTitleSize(0.04);

  f1->GetXaxis()->SetNdivisions(8); // N2*100+N1 (N2=secondary, N1=primary)
  f1->GetYaxis()->SetNdivisions(8); // N2*100+N1 (N2=secondary, N1=primary)

  f1->GetXaxis()->SetLabelSize(.04);
  f1->GetYaxis()->SetLabelSize(.04);

  f1->GetXaxis()->SetLabelOffset(0.01);
  f1->GetYaxis()->SetLabelOffset(0.015);

  f1->GetXaxis()->SetTickLength(0.015);   // default = 0.03
  f1->GetYaxis()->SetTickLength(0.015);   // default = 0.03

  f1->GetXaxis()->SetLabelFont(42);   // default = 62
  f1->GetYaxis()->SetLabelFont(42);   
  f1->GetXaxis()->SetTitleFont(42);
  f1->GetYaxis()->SetTitleFont(42);

  // gStyle->SetHistLineWidth(1);     // Default:1 --- Line width of histogram
  // gStyle->SetLineWidth(.5);        // Default:1 --- Line width of axis.
  // gROOT->ForceStyle(); 

  //  c1->GetFrame()->SetBorderSize(6);      // from root cheat sheet (???)
  //  c1->GetFrame()->SetBorderMode(-1);

// now add some stuff to the graph

  f1->SetLineStyle(1);
  f1->SetLineWidth(1.5);
  f1->Draw();

  f2->SetLineStyle(2);
  f2->SetLineWidth(1.5);
  f2->Draw("same");

  f3->SetLineStyle(3);
  f3->SetLineWidth(1.5);
  f3->Draw("same");

  TLegend* leg = new TLegend(0.2, 0.7, 0.5, 0.85); // x1, y1, x2, y2
  leg->SetTextSize(0.04);
  leg->SetBorderSize(0);
  leg->SetFillColor(0);
  leg->AddEntry(f1, "#alpha=2, #beta=3", "l");  // l for line, f for box
  leg->AddEntry(f2, "#alpha=5, #beta=2", "l");
  leg->AddEntry(f3, "#alpha=2, #beta=2", "l");
  leg->Draw();

}