#include "TFile.h"
#include "TCanvas.h"
#include "TStyle.h"
#include "TH1.h"
#include "TH2.h"
#include "TH3.h"
#include "TGaxis.h"
#include "TRandom.h"
#include "TLegend.h"
#include "TPaveStats.h"

void fitspettro()
{
   TFile *f = TFile::Open("H:/cors/cors_plot.root");
   if (f == 0) {
      // if we cannot open the file, print an error message and return immediatly
      printf("Error: cannot open cors_plot.root!\n");
      return;
   }
   f->ls();
   
   TH1F *hene = (TH1F *)f->Get("hene");
   if (hene == 0) {
      printf("Error getting an histogram from the file!\n");
      return;
   }
   TCanvas *c14 = new TCanvas("c14","hists with different scales",1024,748);
   c14->SetLogx();
   c14->SetLogy();
   hene->SetLineColor(kBlue);
   hene->Draw();
   c14->Update();
   TF1 *fitspettro = new TF1 ("fitspettro","x^(-[0])",0,1000);
   hene->Fit("fitspettro");
   Double_t chi2 = fitspettro->GetChisquare();
   Double_t c0=fitspettro->GetParameter(0);
   Double_t e0=fitspettro->GetParError(0);
   TLegend* leg = new TLegend(0.2, 0.7, .4, .85);
   leg->SetNColumns(1);
   leg->AddEntry(fitspettro, "Fit", "l");
   leg->Draw("same");
   TPaveStats *stats1 = (TPaveStats*)fitspettro->GetListOfFunctions()->FindObject("stats");
   stats1->SetTextColor(kRed);
   stats1->SetX1NDC(0.80); stats1->SetX2NDC(0.98);
   c14->Update;
   
   gROOT->ProcessLine("gROOT->SetBatch()");
   c14.Print("H:/cors/fitspettro.pdf"); delete c14;
   gROOT->ProcessLine("gROOT->SetBatch(kFALSE)");



   
}