Stacked Bars chart

// Use Morris.Bar
Morris.Bar({
  element: 'graph',
  data: [
    {x: 'Raihan', y: 3, z: 2, a: 3},
    {x: 'Samiul', y: 2, z: null, a: 1},
    {x: 'Mamun', y: 0, z: 2, a: 4},
    {x: 'Rashed', y: 2, z: 4, a: 3}
  ],
  xkey: 'x',
  ykeys: ['y', 'z', 'a'],
  labels: ['Y', 'Z', 'A'],
  horizontal: true,
  stacked: true
});