void calc_phi_t_xsec_parameters(int dataset){
  gStyle->SetOptStat(0);
  double eff[50],deff[50];
  double y[50],dy[50];
  double t[50],dt[50];
  double Nps[48];
  double dsdt0[48],ddsdt0[48];
  double tslope[48],dtslope[48];  
  double eff1[50],deff1[50];
  double y1[50],dy1[50];
  double dsdt01[48],ddsdt01[48];
  double tslope1[48],dtslope1[48];

  //  int bin=int((Eg-2.8)/0.2);
  TFile *f=NULL;
  switch(dataset){
  case 0:
    f=TFile::Open("/work/halld/home/staylor/recon/xsecs/flux_51384_51457.root");
    cout << "Flux file:  flux_51384_51457.root" << endl;
    break;
  case 1:
    f=TFile::Open("/work/halld/home/staylor/recon/xsecs/flux_40856_41105.root");
    cout << "Flux file:  flux_40856_41105.root" << endl;
   break;
  case 2:
    f=TFile::Open("/work/halld/home/staylor/recon/xsecs/flux_41106_41257.root");
    cout << "Flux file:  flux_41106_41257.root" << endl;
    break;
  default:
    cout << "No data set specified" << endl;
    break;
  }
  if (f!=NULL){  
    f->cd();
    TH1D *tagged_flux=(TH1D*)f->FindObjectAny("tagged_flux");
    for (int i=0;i<48;i++){
    Nps[i]=tagged_flux->GetBinContent(i+1);
    }
    f->Close();
    
    ofstream phi_parms_file("phi_parms.dat");
    
    for (int bin=0;bin<48;bin++){
      double Nps_sum=Nps[bin];
      //Nps_sum=1e11; 
      ifstream in1("phi_t_yields2.dat");
      for (int i=0;i<bin;i++){
	string skipline;
	getline(in1,skipline);
	//   cout << skipline << endl;
	
      }
      double dummy;
      in1 >> dummy;
      //cout << dummy << endl;
      for (int i=0;i<50;i++){
	in1 >> y[i];
	in1 >> dy[i];
      }
      in1.close();
      ifstream in2("phi_kk_t_acc2.dat"); 
      for (int i=0;i<bin;i++){
	string skipline;
	getline(in2,skipline);
	//   cout << skipline << endl;
	
      }
      in2 >> dummy;
      for (int i=0;i<50;i++){
	in2 >> eff[i];
	//eff[i]=0.5;
	in2 >> deff[i];
      }
      in2.close();
      
      double y_acc[50],dy_acc[50];
      for (int i=0;i<50;i++){
	//cout << eff[i] << endl;
	if (eff[i]>0.){
	  double scale=1e6/1.293/Nps_sum/0.492/0.04;
	  y_acc[i]=scale*y[i]/eff[i];
	  // cout << y[i] << endl;
	  dy_acc[i]=y_acc[i]*sqrt(deff[i]*deff[i]/(eff[i]*eff[i])+dy[i]*dy[i]/(y[i]*y[i]));
	}
	t[i]=0.02+0.04*i;
	dt[i]=0.02;
      }
      
      
      TGraphErrors *g1=new TGraphErrors(35,&t[2],&y_acc[2],&dt[2],&dy_acc[2]);
      TF1 *f1=new TF1("f1","[0]*exp([1]*x)",0.1,1.);
      f1->SetParameters(1,-4);
      g1->Fit(f1,"rq");
      phi_parms_file << 2.9+0.2*bin << " " << f1->GetParameter(0) << " " 
		     << f1->GetParError(0) << " " 
		     << f1->GetParameter(1) << " " 
		    << f1->GetParError(1) << endl;
    }
    phi_parms_file.close();
    
    ofstream phi_parms_file1("phi_parms_method1.dat");
    
    for (int bin=0;bin<48;bin++){
      double Nps_sum=Nps[bin];
      //Nps_sum=1e11; 
      ifstream in3("phi_t_yields.dat");
      for (int i=0;i<bin;i++){
	string skipline;
	getline(in3,skipline);
	//   cout << skipline << endl;
	
      }
      double dummy;
      in3 >> dummy;
      //cout << dummy << endl;
      for (int i=0;i<50;i++){
	in3 >> y1[i];
	in3 >> dy1[i];
      }
      in3.close();
      ifstream in4("phi_kk_t_acc.dat"); 
      for (int i=0;i<bin;i++){
	string skipline;
	getline(in4,skipline);
	//   cout << skipline << endl;
	
      }
      in4 >> dummy;
      double eff1[50],deff1[50];
      for (int i=0;i<50;i++){
	in4 >> eff1[i];
	//eff[i]=0.5;
	in4 >> deff1[i];
      }
      in4.close();
      
      double y_acc1[50],dy_acc1[50];
      for (int i=0;i<50;i++){
	//cout << eff[i] << endl;
	if (eff1[i]>0.){
	  double scale=1e6/1.293/Nps_sum/0.492/0.04;
	  y_acc1[i]=scale*y1[i]/eff1[i];
	  // cout << y[i] << endl;
	  dy_acc1[i]=y_acc1[i]*sqrt(deff1[i]*deff1[i]/(eff1[i]*eff1[i])+dy1[i]*dy1[i]/(y1[i]*y1[i]));
	}
      }
      
      
      TGraphErrors *g2=new TGraphErrors(35,&t[2],&y_acc1[2],&dt[2],&dy_acc1[2]);
      TF1 *f1=new TF1("f1","[0]*exp([1]*x)",0.1,1.);
      f1->SetParameters(1,-4);
      g2->Fit(f1,"rq");
      phi_parms_file1 << 2.9+0.2*bin << " " << f1->GetParameter(0) << " " 
		      << f1->GetParError(0) << " " 
		      << f1->GetParameter(1) << " " 
		      << f1->GetParError(1) << endl;
    }
    phi_parms_file1.close();
    
  }
}