vega-lite：如何将 JSON 中的日期指定为包含年、月和日数字的单独字段？

Question

我的 JSON 数据是一个对象列表，每个对象都包含以下格式的日期：

  "date" : {
    "year" : 2019,
    "month" : 2,
    "day" : 17
  },

如何告诉 Vega-lite 这是约会对象？我通过创建另一个 day 字段来解决这个问题，该字段是一个连接这三个字段的字符串，并使用：

    "format" : {
      "parse" : {
        "day" : "date: '%Y %m %d'"
      }

但我希望能够只使用现有的 3 个字段....

Answer 1

您可以使用计算转换以及 datetime 表达式来执行此操作。例如 (vega-editor link):

{
  "data": {
    "values": [
      {"date": {"year": 2019, "month": 2, "day": 15}, "val": 1},
      {"date": {"year": 2019, "month": 2, "day": 16}, "val": 2},
      {"date": {"year": 2019, "month": 2, "day": 17}, "val": 4},
      {"date": {"year": 2019, "month": 2, "day": 18}, "val": 3},
      {"date": {"year": 2019, "month": 2, "day": 19}, "val": 5},
      {"date": {"year": 2019, "month": 2, "day": 20}, "val": 6}
    ]
  },
  "transform": [
    {
      "calculate": "datetime(datum.date.year, datum.date.month, datum.date.day)",
      "as": "combined"
    }
  ],
  "mark": "area",
  "encoding": {
    "x": {"field": "combined", "type": "temporal"},
    "y": {"field": "val", "type": "quantitative"}
  }
}

vega-lite：如何将 JSON 中的日期指定为包含年、月和日数字的单独字段？

vega-lite: how to specify date in JSON as separate fields containing year, month, and day numbers?

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