来自Datable的json groupby数据

我希望从这里使用这个amCharts库来实现一些可视化。

我已经序列化了我的datatable，但它似乎不起作用，我不确定如何按4个类别/区域分组

任何帮助/建议都会大有帮助

var groupData = [
  {
    "name": "EU member before 2004",
    "color": chart.colors.getIndex(0),
    "data": [
      {
        "title": "Austria",
        "id": "AT", // With MapPolygonSeries.useGeodata = true, it will try and match this id, then apply the other properties as custom data
        "customData": "1995"
      }, {
        "title": "Ireland",
        "id": "IE",
        "customData": "1973"
      }, {
        "title": "Denmark",
        "id": "DK",
        "customData": "1973"
      }, {
        "title": "Portugal",
        "id": "PT",
        "customData": "1986"
      }
    ]
  },
  {
    "name": "Joined at 2004",
    "color": chart.colors.getIndex(1),
    "data": [
      {
        "title": "Lithuania",
        "id": "LT",
        "color": chart.colors.getIndex(1),
        "customData": "2004",
        "groupId": "2004"
      }, {
        "title": "Latvia",
        "id": "LV",
        "color": chart.colors.getIndex(1),
        "customData": "2004",
        "groupId": "2004"
      }
  },
  {
    "name": "Joined at 2007",
    "color": chart.colors.getIndex(3),
    "data": [
      {
        "title": "Romania",
        "id": "RO",
        "customData": "2007"
      }, {
        "title": "Bulgaria",
        "id": "BG",
        "customData": "2007"
      }
    ]
  },
  {
    "name": "Joined at 2013",
    "color": chart.colors.getIndex(4),
    "data": [
      {
        "title": "Croatia",
        "id": "HR",
        "customData": "2013"
      }
    ]
  }
];