void plot_ratio (void)
{
// 
// plot the ratio of response to LED between prototype and pre-production assemblies
//          including non-linearity corrections
//

// #include <TMath.h>
#include <TRandom.h>

gROOT->Reset();
//TTree *Bfield = (TTree *) gROOT->FindObject("Bfield");
gStyle->SetPalette(1,0);
gStyle->SetOptStat(kFALSE);
gStyle->SetOptFit(kTRUE);
gStyle->SetOptFit(1111);
gStyle->SetPadRightMargin(0.15);
gStyle->SetPadLeftMargin(0.15);
gStyle->SetPadBottomMargin(0.15);
gStyle->SetFillColor(0);
//

   char string[256];
   char filename[80];
   Int_t j,jj;
   
   #define npts 4;

   Double_t Vprep_D[npts]={337,676,569,867};
   Double_t Vprot_D[npts]={893,1599,979,1830};
   Double_t Vprep_U[npts]={464,1346,1397,1794};
   Double_t Vprot_U[npts]={936,2440,2246,3350};

   Double_t Vprep_Dcorr[npts];
   Double_t Vprot_Dcorr[npts];
   Double_t Vprep_Ucorr[npts];
   Double_t Vprot_Ucorr[npts];

   Double_t Ratio_D[npts];
   Double_t Ratio_U[npts];


   Double_t meanD=0;
   Double_t meanU=0;

   for (j=0;j<npts;j++) {
          Double_t f1= (25000./((j+1)*57600)*(Vprot_D[j])/4000.);
          Double_t corr1 = f1/(1-exp(-f1));
          Double_t f2 = (25000./((j+1)*57600.)*(Vprep_D[j])/4000.);
          Double_t corr2 = f2/(1-exp(-f2));
          Vprot_Dcorr[j]=Vprot_D[j]*corr1;
          Vprep_Dcorr[j]=Vprep_D[j]*corr2;
          Ratio_D[j] = (Vprot_Dcorr[j])/(Vprep_Dcorr[j]);
          meanD += Ratio_D[j];
          cout <<  "j=" << j << " f1=" << f1 << " corr1=" << corr1 << " Vprot_D=" << Vprot_D[j] << "  Vprot_Dcorr=" << Vprot_Dcorr[j]  << "   f2=" << f2 << "  corr2=" << corr2 << "  Vprep_D=" << Vprep_D[j] << "  Vprep_Dcorr=" << Vprep_Dcorr[j] << "     Ratio_D[j]=" << Ratio_D[j] << endl; 
          }
   meanD /= 4;
   cout << "Mean = " << meanD << "\n" << endl;

   for (j=0;j<npts;j++) {
          Double_t f1= (25000./((j+1)*57600)*(Vprot_U[j])/4000.);
          Double_t corr1 = f1/(1-exp(-f1));
          Double_t f2 = (25000./((j+1)*57600.)*(Vprep_U[j])/4000.);
          Double_t corr2 = f2/(1-exp(-f2));
          Vprot_Ucorr[j]=Vprot_U[j]*corr1;
          Vprep_Ucorr[j]=Vprep_U[j]*corr2;
          Ratio_U[j] = (Vprot_Ucorr[j])/(Vprep_Ucorr[j]);
          meanU += Ratio_U[j];
          cout <<  "j=" << j << " f1=" << f1 << " corr1=" << corr1 << " Vprot_U=" << Vprot_U[j] << "  Vprot_Ucorr=" << Vprot_Ucorr[j] << "   f2=" << f2 << "  corr2=" << corr2 << "  Vprep_U=" << Vprep_U[j] << "  Vprep_Ucorr=" << Vprep_Ucorr[j] << "     Ratio_U[j]=" << Ratio_U[j] << endl; 
          }
   meanU /= 4;
   cout << "Mean = " << meanU << "\n" << endl;

   Double_t x[npts]={1,2,3,4};

   TGraph *ratioD = new TGraph(npts,x,Ratio_D);


   TCanvas *c1 = new TCanvas("c1","c1 plot_ratio",200,10,700,700);
   c1->SetBorderMode(0);
   c1->SetFillColor(0);
   c1->SetGridx();
   c1->SetGridy();

   TLegend *leg = new TLegend(0.15,0.70,0.50,0.95);

   leg->AddEntry(ratioD,"Ratio V(prototype)/V(pre-production)","p");
   ratioD->GetXaxis()->SetRangeUser(0.,5.);
   ratioD->SetMarkerColor(4);
   ratioD->SetMarkerStyle(21);
   ratioD->Draw("Ap");

   leg->Draw();

   sprintf(filename,"plot_ratio_c1.eps");
   c1->SaveAs(filename);
   sprintf(filename,"plot_ratio_c1.png");
   c1->SaveAs(filename);
}