void graph_var_markers(TGraph *gr, double *size, double *col, double* type)
{
   Int_t np = gr->GetN();

   TMarker *m = new TMarker();

   gr->SetMarkerStyle(1);
   gr->SetMarkerColor(0);
   gr->Draw("AP");

   Double_t *gx = gr->GetX();
   Double_t *gy = gr->GetY();

   for (Int_t i =0; i < np; i++) {
      m->SetMarkerSize(size[i]);
      m->SetMarkerColor(col[i]);
      m->SetMarkerStyle(type[i]);
      m->DrawMarker(gx[i], gy[i]);
   }
}

void graph_var_points () {

   const int np = 6;
   TCanvas *c = new TCanvas();
   double size[np] = {1, 2 ,3 ,4 ,5 ,6};
   double col[np]  = {6, 5, 4, 3, 2, 1};
   double type[np] = {20, 21, 22, 23, 29, 33};

   TGraph *gr = new TGraph(np);

   for (Int_t i =0; i < np; i++) {
      Double_t x = ((Double_t)(i+1))*0.5;
      Double_t y = TMath::Sin(x);
      gr->SetPoint(i, x, y);
   }

   graph_var_markers(gr, size, col, type);

}