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

Double_t coseno(Double_t *x, Double_t *par)
   {
      Float_t xx =x[0];
      Double_t f = par[0]*TMath::Power(TMath::Cos(xx),par[1]);
      return f;
   }
   void angolo()
   {
      TF1 *f1 = new TF1("angolo",coseno,0,2,2);
      f1->SetParameters(2,2);
      f1->SetParNames("ampiezza","esponente");
      f1->Draw();
   }
void myfit()
{
  TF1 *f1=gROOT->GetFunction("angolo");
  f1->SetParameters(73,2);
  c1 = new TCanvas("c1","Distribuzione angolare raggi cosmici",200,10,700,500);
  static const Int_t n = 7;
  Double_t x[n]  = {0,0.2268,0.5235,0.8028,1.0821,1.3089,1.5707};
  Double_t ex[n]  = {0,0,0,0,0,0,0};
  Double_t ey[n] = {9,8,8,6,4,3,2};
  Double_t y[n] = {85,63,63,37,14,12,4};
  gr = new TGraphErrors(n,x,y,ex,ey);
  gr->SetTitle("Distribuzione angolare raggi cosmici");
  gr->SetMarkerColor(2);
  gr->SetMarkerStyle(21);
  gr->SetDirectory(0);
  gr->Draw("AP");
  gr->Fit("angolo");
  Double_t Chisquare = f1->GetChisquare();
  Double_t NDF = f1->GetNDF();
  cout<<"Chi quadro ridotto"<<" = "<<Chisquare/NDF<<endl;    
  c1->SaveAs("ptresVSpt.ps");
  return c1;
}