\psdots[linecolor=blue,dotstyle=triangle,
          dotscale=2](0,0.5)(1,2)(2.8,1.5)
  \pscurve[linecolor=cyan,showpoints=true]
          {->}%
          (0,1.2)(1.3,1.8)(3,0.4)(0.5,0.2)
  \psarc(2,1.5){1}{180}{320}
  \parabola[linecolor=red]{<->}%
           (0.3,0.3)(1.5,1.5)