//Graph constructor reading input from filename.
//filename is assumed to contain at least two columns of numbers.
//the string format is by default "%lg %lg".
//this is a standard c formatting for scanf. If columns of numbers should be
//skipped, a "%*lg" or "%*s" for each column can be added,
//e.g. "%lg %*lg %lg" would read x-values from the first and y-values from
//the third column.
//For files separated by a specific delimiter different from ' ' and '\t' (e.g. ';' in csv files)
//you can avoid using %*s to bypass this delimiter by explicitly specify the "option" argument,
//e.g. option=" \t,;" for columns of figures separated by any of these characters (' ', '\t', ',', ';')
//used once (e.g. "1;1") or in a combined way (" 1;,;;  1").
//Note in that case, the instanciation is about 2 times slower.


{
  	 
  	TFile f("Plot_DataThief.root","RECREATE"); 
	  
    TCanvas c("c", "Grafico Random", 700, 500);
	
    TTree t("t","a simple tree");

  	TGraphErrors g("Christensen_1977.txt", "%lg %lg %lg %lg");
    TGraphErrors h("Patterson_1971.txt", "%lg %lg %lg %lg");
  	
    g.GetXaxis()->SetTitle("E_{c.m.} [MeV]");
    g.GetYaxis()->SetRangeUser(1e19,2e20);
  	g.GetYaxis()->SetTitle("S(E) [MeV barn]");
  	g.SetTitle("Plot DataThief");
  	g.SetMarkerStyle(25);
  	g.SetMarkerColor(3);
  	g.Draw("ap");


  	h.SetMarkerStyle(27);
  	h.SetMarkerColor(4);
  	h.Draw("P");
    h.Draw("E1");

  	t.Write();
  	
  	f.Close();

}