[ROOT] Plotting graph

From: Sam Abraham (abraham@mail.desy.de)
Date: Thu Feb 01 2001 - 14:28:25 MET


Hi
I am trying to plot a graph. I have got a data file with 2 colums of data
 (4000 value each) and i would like to plot a graph  with the first
colomun of data against
the second. I am using as a starting line the program from the tutorials
"example of a graph with errors bars" but i don't know how to include my
set of data in the root program. In the tutorial, the values are directly
typed in the program. Ex: Float_t y[n]={1,2.9,5.6,7.4,9,9.6,8.7,6.3,4.5,1}; 
I would like to know how to replace these values by calling my datafile.



My code is the following;

{
   //
   //
   gROOT->Reset();
   ifstream in;
   in.open("data01.dat",ios::in);
   Float_t x0,x1;

   c1 = new TCanvas("c1"," Graph ",200,10,700,500);

   c1->SetFillColor(42);
   c1->SetGrid();
   c1->GetFrame()->SetFillColor(21); 
   c1->GetFrame()->SetBorderSize(12);
   Int_t n = 4000;
   
 
 ///

///   Float_t y[n]  = ?
///   Float_t y[n]  = ?
   
   
   
   gr = new TGraph(n,x,y);
   gr->SetMarkerColor(4);
   gr->SetMarkerStyle(21);
   gr->Draw("AP");
   
   c1->Update();
}



Cheers, Sam.



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