//Create and Draw a TMultiGraph
//Author:: Rene Brun
#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"
#include "TGraph.h"

void multigraph() {
   gStyle->SetOptFit();
   TCanvas *c36 = new TCanvas("c36","multigraph",700,500);
 //  c36->SetGrid();
  gStyle->SetOptFit(0001);


      // draw a frame to define the range
   TMultiGraph *mg = new TMultiGraph();
     TGraphErrors *gr1 = new TGraphErrors("H:/cors/dati2.txt","a:c");
   gr1->SetMarkerColor(kBlue);
   gr1->SetMarkerStyle(21);
   gr1->Fit("pol1","q");
   gr1->SetTitle("Energia primario- densita'"); 
   gr1->GetXaxis()->SetTitle("Energia (GeV)"); 
     gr1->GetYaxis()->SetTitle("Densita'(#/m^2)"); 
   mg->Add(gr1);

      // create second graph
    TGraphErrors *gr2 = new TGraphErrors("H:/cors/dati2.txt","a:c");
   gr2->SetMarkerColor(kYellow);
   gr2->SetMarkerStyle(20);
   gr2->Fit("pol1","q");
   
   mg->Add(gr2);
   
   mg->Draw("ap");
   
     //force drawing of canvas to generate the fit TPaveStats
   c36->Update();
   TLegend* leg = new TLegend(0.2, 0.7, .4, .85);
   leg->SetNColumns(1);
   leg->AddEntry(gr1, "distanza 10 m", "l");
   leg->AddEntry(gr2, "distanza 100 m", "l");
   leg->Draw("same");
   TPaveStats *stats1 = (TPaveStats*)gr1->GetListOfFunctions()->FindObject("stats");
   TPaveStats *stats2 = (TPaveStats*)gr2->GetListOfFunctions()->FindObject("stats");
   stats1->SetTextColor(kBlue); 
   stats2->SetTextColor(kYellow); 
   stats1->SetX1NDC(0.12); stats1->SetX2NDC(0.32); stats1->SetY1NDC(0.75);
   stats2->SetX1NDC(0.72); stats2->SetX2NDC(0.92); stats2->SetY1NDC(0.78);
   c36->Modified();
   gROOT->ProcessLine("gROOT->SetBatch()");
   c36.Print("H:/cors/gamma_ene-dens.pdf"); delete c36;
   gROOT->ProcessLine("gROOT->SetBatch(kFALSE)");
}