#include <TH1F.h>
#include <TFile.h>
#include <TTree.h>
#include <Riostream.h>

Double_t poisson(Double_t *x, Double_t *par)
   {
      Float_t xx =x[0];
      Double_t f = par[0]*(TMath::Poisson(xx,par[1]));
      return f;
   }
   void cosmics()
   {
      TF1 *f1 = new TF1("cosmics",poisson,0,150,2);
      f1->SetParameters(2,1);
      f1->SetParNames("coefficiente","media");
      f1->Draw();
   }
void myfit()
{
  TF1 *f1=gROOT->GetFunction("cosmics");
  f1->SetParameters(5,5);
  ifstream in;
  in.open("dati.dat");
  Double_t amplitude;
  TFile *f = new TFile("amplitude.root","RECREATE");
  TH1F *h1 = new TH1F("h1","amplitude distribution",7,0,12);
  while (1) {
    if (!in.good()) break;
	in >> amplitude;
	cout << amplitude << endl;
     h1->Fill(amplitude);
}
  in.close();
  h1->Fit("cosmics");
  Double_t Chisquare = f1->GetChisquare();
  Double_t NDF = f1->GetNDF();
  cout<<"Chi quadro ridotto"<<" = "<<Chisquare/NDF<<endl;
  f->Write();
  f->Close();
}