function vis_binclass_dataset(d)
  hold on;

  nclasses = max(d(:,3));
  assert(nclasses<4, 'As of now, works for 1-3 classes.')

  markerstyle={'rx','bo','g^'};
  for ic=1:nclasses
    s=d(:,3)==ic;
    plot(d(s,1),d(s,2),markerstyle{ic}, 'MarkerSize',6); 
  end

