void graph() {
   //Draw a simple graph
   // To see the output of this macro, click begin_html <a href="gif/graph.gif">here</a>. end_html
   //Author: Rene Brun
   gROOT->init();
   TCanvas *c1 = new TCanvas("c1","access number",200,10,700,500);

   c1->SetFillColor(42);
   c1->SetGrid();

   ifstream ifile;
   Int_t data[1000];
   Int_t nlines = 0;
   ifile.open("access.dat");
   while(1) {
	ifile >> data[nlines];
	nlines++;
	if(!ifile.good())
		break;
   }
   ifile.close();
   const Int_t n = 135;
   Int_t x[n], y[n];
   for (Int_t i=0;i<n;i++) {
     x[i] = i;
     y[i] = data[i];
     printf(" i %i %d %d \n",i,x[i],y[i]);
   }
   gr = new TGraph(n,x,y);
   gr->SetLineColor(2);
   gr->SetLineWidth(4);
   gr->SetMarkerColor(4);
   gr->SetMarkerStyle(21);
   gr->SetTitle("access number of this site");
   gr->GetXaxis()->SetTitle("days");
   gr->GetYaxis()->SetTitle("The access number");
   gr->Draw("AC");
	gr->Fit("pol2", "V");
   // TCanvas::Update() draws the frame, after which one can change it
   c1->Update();
   c1->GetFrame()->SetFillColor(21);
   c1->GetFrame()->SetBorderSize(12);
   c1->Modified();
}