#include <TMath.h>

Double_t GaussFunct (Double_t* x, Double_t* par)
{
  return exp(-0.5*pow((x[0]-par[0])/par[1],2))/
    (par[1]*sqrt(2*TMath::Pi()));
}



 Double_t Fattoriale (Int_t x)
 {
   if (x<=1) return 1.0;
   return x*Fattoriale(x-1);
 }



Double_t PoissonFunct (Int_t x, Int_t media)
{
  return pow(media,x)*exp(-media)/Fattoriale(x);
}


void GaussPoiss()
{
  gROOT->Reset();
  const Int_t nEv = 10000;
  const Int_t xMin = 5;
  const Int_t xMax = 45;
  
   Double_t ParPoiss = 25.0;

   Double_t ParGaus[2] = {25.0,5.0}; 
  
  gRandom->SetSeed(0);

 
    TCanvas* c1 = new TCanvas("c1","Gauss",180,10,700,500);
    TCanvas* c2 = new TCanvas("c2","Poisson",200,30,700,500);
 

 // Calcolo i valori della  poissoniana

  Double_t x[xMax-xMin+1], y[xMax-xMin+1];
  for (Int_t i = 0; i<xMax-xMin+1; i++)
    {
      x[i] = xMin + i;
      y[i] = PoissonFunct (x[i],ParPoiss);
    }




  c1->cd();
  TF1* Gauss2PDF = new TF1("Gauss2PDF",GaussFunct,xMin,xMax,4);
  Gauss2PDF->SetParameters (ParGaus);
  Gauss2PDF->SetLineColor(8);
  Gauss2PDF->Draw("");



// Disegno la poisson nella seconda canvas
  c2->cd();
  TGraph* Poisson1PDF = new TGraph (xMax-xMin+1,x,y);
  Poisson1PDF->SetFillColor(35);
  Poisson1PDF ->SetTitle("Poisson");
  Poisson1PDF->SetMarkerStyle(21);
  Poisson1PDF->SetMarkerColor(4);
  Poisson1PDF->Draw("APC");





    TCanvas* all = new TCanvas ("all","All in one");
    all->cd();
    Poisson1PDF->Draw("APC");
    Gauss2PDF->Draw("same");
 
}