Vega-Lite：我可以合并数据源吗？

Question

我有以下格式的时间序列数据：

    "data": {"values":[
    {"time":nnn,"Pressure":1},
    {"time":nnn,"Pressure":2},
    {"time":nnn,"Pressure":3}
    ] }

，另一个为：

        "data": {"values":[
        {"time":nnn,"Flow":1},
        {"time":nnn,"Flow":2},
        {"time":nnn,"Flow":3}
        ] }

如果时间戳相同，如何将其合并为一个数组：

        "data": {"values":[

        {"time":nnn,"Pressure":1,"Flow":1},
        {"time":nnn,"Pressure":2,"Flow":2},
        {"time":nnn,"Pressure":3,"Flow":3}

        ] },

Answer 1

您可以使用Lookup Transform联接数据集。这是一个使用与问题（view in vega editor）中类似的数据的快速示例：

{
  "datasets": {
    "data1": [
      {"time": 0, "Pressure": 1},
      {"time": 1, "Pressure": 2},
      {"time": 2, "Pressure": 3}
    ],
    "data2": [
      {"time": 0, "Flow": 1},
      {"time": 1, "Flow": 2},
      {"time": 2, "Flow": 3}
    ]
  },
  "data": {"name": "data1"},
  "transform": [
    {
      "lookup": "time",
      "from": {"data": {"name": "data2"}, "key": "time", "fields": ["Flow"]}
    }
  ],
  "mark": "line",
  "encoding": {
    "x": {"field": "Pressure", "type": "quantitative"},
    "y": {"field": "Flow", "type": "quantitative"}
  }
}