Vega-Lite 分层图表 : how to get tick marks and tick labels to span the entire axis?

Question

我正在制作一个分层图表，其中有条形图和规则线。我遇到的问题是，在 x 轴上，刻度线和刻度标签只出现在条形图下方，不会跨越整个轴，因此在规则线下方没有刻度线和标签位于。这是我所看到的示例 ( link to Vega editor ):

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "data": {"url": "data/movies.json"},
  "transform": [
  {"calculate": "2*datum.IMDB_Rating", "as": "UpperLimit"}
  ],
  "layer": [
    {
      "mark": "bar",
      "encoding": {
        "x": {"bin": true, "field": "IMDB_Rating", "type": "quantitative"},
        "y": {"aggregate": "count", "type": "quantitative"}
      }
    },
    {
      "mark": "rule",
      "encoding": {
        "x": {
          "aggregate": "max",
          "field": "UpperLimit",
          "type": "quantitative"
        },
        "color": {"value": "red"},
        "size": {"value": 5}
      }
    }
  ]
}

Image of issue

如何让刻度线和标签跨越整个轴？在此先感谢您的帮助!

Answer 1

当您在编码中使用 bin 变换时，Vega-Lite 会调整默认轴属性以匹配 binning。您可以通过编码的 scale 和 axis 属性手动重新调整这些，但我认为更简单的方法是将 bin 转换移动到图表的 transform规范。这是一个示例 ( Vega Editor ):

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "data": {"url": "data/movies.json"},
  "transform": [
    {"calculate": "2*datum.IMDB_Rating", "as": "UpperLimit"},
    {
      "bin": true,
      "field": "IMDB_Rating",
      "as": ["IMDB_Rating_0", "IMDB_Rating_1"]
    }
  ],
  "layer": [
    {
      "mark": "bar",
      "encoding": {
        "x": {
          "field": "IMDB_Rating_0",
          "type": "quantitative",
          "bin": "binned"
        },
        "x2": {"field": "IMDB_Rating_1"},
        "y": {"aggregate": "count", "type": "quantitative"}
      }
    },
    {
      "mark": "rule",
      "encoding": {
        "x": {
          "aggregate": "max",
          "field": "UpperLimit",
          "type": "quantitative"
        },
        "color": {"value": "red"},
        "size": {"value": 5}
      }
    }
  ]
}