#include "TGraphErrors.h"
#include "TCanvas.h"
#include "TH1D.h"
#include <iostream>                                                                                             
#include <fstream>



void Fit_PRD2020()
{

 const Int_t n = 4; // number of data points
  Double_t x[n] ={0};
  Double_t y[n]={0.0};
  Double_t ex[n]={0.0};
  Double_t ey[n]={0.0};
  
  
  
ifstream in("PRD_gate244_2020.txt"); // name of the input file Timewalk_60Co_Run11_gate344.dat

if(!in) {
  cout << "Cannot open input file!!!" << endl;
}
if(in){
    
  for(int i = 0; i<n ; i++){
    
    in >> x[i] >> y[i]  >> ey[i];
  }
  in.close();
}
  
  for(int i = 0; i<n ; i++){
    
    cout << x[i] << "," << " " << y[i] << "," << " " << ey[i] << endl;
  }


{
  TGraphErrors *p = new TGraphErrors("PRD_gate244_2020.txt", "%lg %lg %lg"); 
   TGraphErrors *p1 = new TGraphErrors("PRD_gate344_2020.txt", "%lg %lg %lg");
  TF1 *fit = new TF1("fit", "[0]/sqrt([1]+x) + [2]*x + [3]", 0., 1600.);
  fit->SetLineColor(kRed);
 fit->SetParameters(0.5, 1.0, 7.0, 7.0);
 //fit->SetParameters(75.0,82,83,83);
  p->Fit(fit, "");
  p->SetName("Stopbranch");
  p->SetTitle("Startbranch"); 
  p->Draw();
  fit->SetLineColor(kGreen);
  fit->SetParameters(75.0,82,83,83);
  p1->SetName("Startbranch");
  p1->Fit(fit, "");
  p1->Draw("same");

}

}