root/html/mathBeta_8C.html

#include "TMath.h"
#include "TCanvas.h"
#include "TF1.h"
#include "TLegend.h"
void mathBeta() {
   TCanvas *c1=new TCanvas("c1", "TMath::BetaDist",600,800);
   c1->Divide(1, 2);
   TVirtualPad *pad1 = c1->cd(1);
   pad1->SetGrid();
   TF1 *fbeta = new TF1("fbeta", "TMath::BetaDist(x, [0], [1])", 0, 1);
   fbeta->SetParameters(0.5, 0.5);
   TF1 *f1 = fbeta->DrawCopy();
   f1->SetLineColor(kRed);
   f1->SetLineWidth(1);
   fbeta->SetParameters(0.5, 2);
   TF1 *f2 = fbeta->DrawCopy("same");
   f2->SetLineColor(kGreen);
   f2->SetLineWidth(1);
   fbeta->SetParameters(2, 0.5);
   TF1 *f3 = fbeta->DrawCopy("same");
   f3->SetLineColor(kBlue);
   f3->SetLineWidth(1);
   fbeta->SetParameters(2, 2);
   TF1 *f4 = fbeta->DrawCopy("same");
   f4->SetLineColor(kMagenta);
   f4->SetLineWidth(1);
   TLegend *legend1 = new TLegend(.5,.7,.8,.9);
   legend1->AddEntry(f1,"p=0.5  q=0.5","l");
   legend1->AddEntry(f2,"p=0.5  q=2","l");
   legend1->AddEntry(f3,"p=2    q=0.5","l");
   legend1->AddEntry(f4,"p=2    q=2","l");
   legend1->Draw();
   TVirtualPad *pad2 = c1->cd(2);
   pad2->SetGrid();
   TF1 *fbetai=new TF1("fbetai", "TMath::BetaDistI(x, [0], [1])", 0, 1);
   fbetai->SetParameters(0.5, 0.5);
   TF1 *g1=fbetai->DrawCopy();
   g1->SetLineColor(kRed);
   g1->SetLineWidth(1);
   fbetai->SetParameters(0.5, 2);
   TF1 *g2=fbetai->DrawCopy("same");
   g2->SetLineColor(kGreen);
   g2->SetLineWidth(1);
   fbetai->SetParameters(2, 0.5);
   TF1 *g3=fbetai->DrawCopy("same");
   g3->SetLineColor(kBlue);
   g3->SetLineWidth(1);
   fbetai->SetParameters(2, 2);
   TF1 *g4=fbetai->DrawCopy("same");
   g4->SetLineColor(kMagenta);
   g4->SetLineWidth(1);
   TLegend *legend2 = new TLegend(.7,.15,0.9,.35);
   legend2->AddEntry(f1,"p=0.5  q=0.5","l");
   legend2->AddEntry(f2,"p=0.5  q=2","l");
   legend2->AddEntry(f3,"p=2    q=0.5","l");
   legend2->AddEntry(f4,"p=2    q=2","l");
   legend2->Draw();
   c1->cd();
}