#include "Riostream.h"

void Ascii2root(const char *fname = "eff_6.dat")
{
   if (!(fname && fname[0])) return; // just a precaution
   auto a = TFile::Open("eff_6.root","RECREATE");
   TGraph *g = new TGraph(fname);
   Int_t n = g->GetN(); // get the no. of points
   if (n < 2) { delete g; return; } // just a precaution
   // g->Sort(); // just a precaution
  
   Double_t *x = new Double_t[(n + 1)];
   x[0] = (3.0 * g->GetX()[0] - g->GetX()[1]) / 2.0;
   x[n] = (3.0 * g->GetX()[(n - 1)] - g->GetX()[(n - 2)]) / 2.0;
   for (Int_t i = 1; i < n; i++) {
      x[i] = (g->GetX()[(i - 1)] + g->GetX()[i]) / 2.0;
   }
   TH1D *h = new TH1D("h", "spectrum;x-value(Channels);#counts", n, x);
   delete [] x; // no longer needed
  
   h->FillN(n, g->GetX(), g->GetY());
   delete g; // no longer needed
   h->Sumw2(kFALSE); // make sure "bin_error = sqrt(bin_content)"
   //h->ResetStats(); // reset the statistics including the number of entries
   //h->Print("All");
   //h->Draw();
   h->Write();
   a->Close();
   delete a;
}