使用 Vega Lite 显示已经聚合的数据

Question

我正在尝试显示总和随时间变化的堆积条形图。数据看起来像这样：

[
  {
    "date": 12345,
    "sumA": 100,
    "sumB": 150
  },
  ...
]

我正在将 x 轴编码到字段 "date"。我需要将日期为 12345 的柱堆叠起来，一部分高度为 100，另一部分以另一种颜色显示，高度为 150。

Vega Lite seems to expect the raw data，但这太慢了。我在服务器端进行聚合以节省时间。我可以像上面的示例一样用勺子喂 Vega Lite 聚合体吗？

Answer 1

您可以使用 fold transform to fold your two columns into one, and then the channel encodings take care of the rest. For example (vega editor):

{
  "data": {
    "values": [
      {"date": 1, "sumA": 100, "sumB": 150},
      {"date": 2, "sumA": 200, "sumB": 50},
      {"date": 3, "sumA": 80,  "sumB": 120},
      {"date": 4, "sumA": 120, "sumB": 30},
      {"date": 5, "sumA": 150, "sumB": 110}
    ]
  },
  "transform": [
    {"fold": ["sumA", "sumB"], "as": ["column", "value"]}
  ],
  "mark": {"type": "bar"},
  "encoding": {
    "x": {"type": "ordinal", "field": "date"},
    "y": {"type": "quantitative", "field": "value"},
    "color": {"type": "nominal", "field": "column"}
  }
}

使用 Vega Lite 显示已经聚合的数据

Using Vega Lite to display already-aggregated data

vega-lite