void Calib()
{

    TGraph *gr1 = new TGraph(); 

    TCanvas *c1=new TCanvas("MB","Calibration Curve",100,100,900,500);
   


    fstream file;
    file.open("Core_CristalA_Calib.txt", ios::in);
    
    
    float Channel, Energy;
    
    
    
    while(1)
    {
    
    file >> Channel >> Energy;
    gr1->SetPoint(gr1->GetN(), Channel, Energy);
 
    if(file.eof()) break;
    
    
 
    }
    
    file.close();
    
    TF1 *fit_1 = new TF1("fit_1","pol1");    //       <-------------- calib function
    gr1->Fit(fit_1,"","",40,16000); 
    fit_1->SetLineWidth(2); //width of fit line
    fit_1->SetLineColor(kBlue);
    fit_1->SetLineStyle(2);
    
    c1->GetTickx();
    c1->GetTicky();
    c1->SetGridx();
    c1->SetGridy();
    c1->Divide(1,2);
    c1->cd(1);
    gr1->Draw("A*");
    gr1->GetXaxis()->SetTitle("Channel");
    gr1->GetYaxis()->SetTitle("Energy(kev)");
    
    float a,b,c;
    a=fit_1->GetParameter(0); //off
    
    b=fit_1->GetParameter(1); //gain
    c=0.0;
    // c=fit_1->GetParameter(2);  //gain2        //             <----------------- ATTENTION
    
    
    
    float cal=0;
    for(Int_t l = 0 ; l<(int)(Channel.size());l++){
                                              for(Int_t k = 0 ; k<(int)(Energy.size());k++){
							cal=cal+Energy.at(k)-(Channel.at(l)*b+a);
						
						}
						
	
	}
	
	TGraph *gr2 = new TGraph(14,Energy.at(k),cal.at(k));
	
	/*
    float cal[14];
 	for(Int_t i=0 ; i<14;i++){
		cal[i]=Energy[i]-(Channel[i]*Channel[i]*c+Channel[i]*b+a);
		printf("%f\n",Channel[i]*Channel[i]*c);
	}   
	*/
    
    
    c1->cd(2);
    gr2->Draw("A*");
    gr2->GetXaxis()->SetTitle("Channel");
    gr2->GetYaxis()->SetTitle("Residuals(kev)");

    TF1 *fit_2 = new TF1("fit_2","pol0");
    fit_2->SetLineWidth(2); //width of fit line
    fit_2->SetLineColor(kBlue);
    fit_2->SetLineStyle(2);
    gr2->Fit(fit_2,"","",10,30000);
    //gr2->Fit("pol0","","",10,30000);  //direct way of writing the zero degree polynomial line

    printf("Result [offset] [gain] [quadratic gain] %f %f %e\n",a,b,c);
    














}