#include <time.h>

void macro_ex() {

   TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500);

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

   const Int_t max = 10;

   Double_t x[max];
   Double_t y[max];
   Double_t bw;

   Double_t c=0;
   x[0]=0;
   y[0]=0;
   stringstream temp;
   string datetime;
   const char *p;

   gr = new TGraph(1,x, y);
   gr->SetMarkerStyle(21);
   gr->SetTitle("Time graph");
   gr->GetXaxis()->SetTitle("X title");
   gr->GetYaxis()->SetTitle("Y title");
   Int_t i =0;
   gr->Draw("ALP");

   while (1) {
      if (i==max){
         i=0;
         gr->Set(i);
      }
      t = time(0);
      timeinfo = localtime ( &t );
      temp << timeinfo->tm_hour << ":" << timeinfo->tm_min <<":" << timeinfo-> tm_sec;
      datetime = temp.str();
      p = datetime.c_str();

      x[i] = t;
      if (i%2 == 0) {  // only to draw triangles
         y[i] = 2000;
      } else {
         y[i] = 2;
      }

      gr->SetPoint(i,x[i]-x[0],y[i]);

      if (i==0) {
         gr->GetXaxis()->Set(1,-0.1,0.1);
      } else {
	 bw = ((x[i]-x[0])/(i+1))/2.;
         gr->GetXaxis()->Set(i+1,-bw,x[i]-x[0]+bw);
      }
      gr->GetXaxis()->SetNdivisions(-(i+1));

///  The value of "p" is wrong, it cumulates all the dates. This should be revisited      
///      gr->GetXaxis()->SetBinLabel(i+1,p);
      
/// This kind of loop is neede to define the labels.
      for (Int_t j=1; j<=i+1; j++) {
         gr->GetXaxis()->SetBinLabel(j,Form("j=%d",j));
      }

      c1->Update();
      gSystem->Sleep(1000);
      i= i+1;
   }
}