#include "TCanvas.h"
#include "TGraph.h"
#include "TMath.h"
#include "TMarker.h"
void graph_var_points()
{
	Int_t np = 6;
	TCanvas *c = new TCanvas();
	TGraph *gr = new TGraph(np);
	TMarker *marks[np];
	// make it invisible
	gr->SetMarkerStyle(1);
	gr->SetMarkerColor(0);
	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);
	}
	gr->Draw("A*");
	Double_t *gx = gr->GetX();
	Double_t *gy = gr->GetY();
	for (Int_t i =0; i < np; i++) {
		marks[i]= new TMarker(gx[i],gy[i], 20);
		marks[i]->SetMarkerSize(gy[i]*3);
		marks[i]->SetMarkerColor((i+1)%7);
		marks[i]->Draw(); 
	}
	c->Modified();
	c->Update();
}