#include "TFile.h"
#include "TGraphErrors.h"
#include "TF1.h"

Double_t Fit1(Double_t *x, Double_t *par)
{
        Double_t arg1     = TMath::Log(0.01*x[0]);          // in keV
        Double_t arg2     = TMath::Log(0.001*x[0]);          // in keV

            Double_t fit_val = TMath::Exp(TMath::Power((TMath::Power((par[0]+par[1]*arg1+par[2]*arg1*arg1),(-1.0*par[3]))+TMath::Power((par[4]+par[5]*arg2+par[6]*arg2*arg2),(-1.0*par[3]))),(-1.0*1/par[3])))/1000.;
        return fit_val;
}
void efficiency_R() {
   TGraphErrors *g = new TGraphErrors("effvsE.txt", "%lg %lg %lg");
   TF1 *RT = new TF1("RT",Fit1,100.,1500.,7.);
   RT->SetParameter(0,13.);
   RT->SetParameter(1,-0.3);
   RT->FixParameter(2,0.);
   RT->FixParameter(3,15.);
   RT->SetParameter(4,5.);
   RT->SetParameter(5,5.);
   RT->SetParameter(6,10.);

   RT->Draw("L");
   g->Fit("RT","IER");
   g->SetMarkerStyle(3);
   g->Draw("AP");
   g->SetTitle("Efficiency Vs Energy(keV);Energy;Efficiency");
   gStyle->SetOptFit(0111);  //showing the parameters on graph
   double par[7];
   RT->GetChisquare();
   RT->GetParameters(par);
}