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

Double_t life(Double_t *x, Double_t *par)
   {
      Float_t xx = x[0];
      Double_t f = par[0]*(exp(-xx/par[1])+exp(-xx/par[2]));
      return f;
   }
   void mu()
   {
      TF1 *f1 = new TF1("mu",life,0,1000,3);
      f1->SetParameters(20,10,200);
      f1->SetParNames("coefficiente","meanlife1","meanlife2");
      f1->Draw();
   }
void myfit()
{
  TF1 *f1=gROOT->GetFunction("mu");
  f1->SetParameters(200,100,2000);
  ifstream in;
  in.open("vitamu.txt");
  Double_t mlife;
  TFile *f = new TFile("mlife.root","RECREATE");
  TH1F *h1 = new TH1F("h1","mlife distribution",100,0,1000);
  while (1) {
    if (!in.good()) break;
	in >> mlife;
	cout << mlife << endl;
     h1->Fill(mlife);
}
  in.close();
  h1->Fit("mu");
  Double_t Chisquare = f1->GetChisquare();
  Double_t NDF = f1->GetNDF();
  cout<<"Chi quadro ridotto"<<" = "<<Chisquare/NDF<<endl;
  f->Write();
  f->Close();
}