Morris.Donut({
  element: 'grafico',
  data: [
    {label: "Referral", value: 42.7},
    {label: "Direct", value: 8.3},
    {label: "Social", value: 12.8},
    {label: "Organic", value: 36.2}
  ],
  formatter: function (y) { return y + "%" ;}
});