},
    {x: '2014-06-20', y: 10, group: 1},
    {x: '2014-06-21', y: 20, group: 2},
    {x: '2014-06-22', y: 600, group: 2},
    {x: '2014-06-23', y: 100, group: 2},
    {x: '2014-06-24', y: 250, group: 2},
    {x: '2014-06-25', y: 300, group: 2},
    {x: '2014-06-26', y: 200, group: 3},
    {x: '2014-06-27', y: 600, group: 3},
    {x: '2014-06-28', y: 1000, group: 3},
    {x: '2014-06-29', y: 250, group: 3},
    {x: '2014-06-30', y: 300, group: 3}
  ];

  var dataset = new vis.DataSet(items);
  var options 