Highcharts stack column data

series: [
  {
    name: 'name1',
    stack: 'aaa',
    data: [
      [Date.parse('2014-06-30'), 5],
      [Date.parse('2014-07-01'), 3],
      [Date.parse('2014-07-02'), 4],
      [Date.parse('2014-07-03'), 7],
      [Date.parse('2014-07-04'), 2]
    ]
  }, {
    name: 'name2',
    stack: 'aaa',
    data: [
      [Date.parse('2014-06-30'), 5],
      [Date.parse('2014-07-01'), 3],
      [Date.parse('2014-07-02'), 4],
      [Date.parse('2014-07-03'), 7],
      [Date.parse('2014-07-04'), 2]
    ]
  }, {
    name: 'name3',
    stack: 'bbb',
    data: [
      [Date.parse('2014-06-30'), 5],
      [Date.parse('2014-07-01'), 3],
      [Date.parse('2014-07-02'), 4],
      [Date.parse('2014-07-03'), 7],
      [Date.parse('2014-07-04'), 2]
    ]
  }, {
    name: 'name4',
    stack: 'bbb',
    data: [
      [Date.parse('2014-06-30'), 5],
      [Date.parse('2014-07-01'), 3],
      [Date.parse('2014-07-02'), 4],
      [Date.parse('2014-07-03'), 7],
      [Date.parse('2014-07-04'), 2]
    ]
  }
]