vega-lite - 如何根据条件更改 vega-lite 中的线条描边颜色

Question

我在 vega-lite 中有一个图表，并尝试根据绿色阴影区域的上限 (obeGrenze) 更改点和线的颜色，例如，如果点高于此上限，则将颜色设置为红色。代码：

    {
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "description": "A dual axis chart, created by setting y's scale resolution to `\"independent\"`",
  "width": 300, "height": 300,
  "data": {
    "url": "https://pnwscm60.github.io/data/chdeath.csv"
  }, 
  "axis": {
    "font": "Open Sans Condensed"
  },
  "encoding": {
    "x": {
        "field": "date",
        "axis": {"format": "%d.%m", "title": null},
        "type": "temporal",
        "timeUnit": "daymonth"
    }
  },
  "layer": [
    {
      "mark": {"opacity": 0.3, "type": "area", "color": "#85C5A6"},
      "transform": [{"filter": "datum.Alter == \"65\""}],
      "encoding": {
        "y": {
          "aggregate": "average",
          "field": "obeGrenze",
          "scale": {"domain": [0, 1800]},
          "type": "quantitative",
          "axis": {"title": "Anzahl wöchentliche Todesfälle", "titleColor": "#111","format": ".2r"}
        },
        "y2": {
          "aggregate": "average",
          "field": "untGrenze"
        }
      }
    },
    {
      "mark": {"opacity": 0.3, "type": "area", "color": "#85C5A6"},
      "transform": [{"filter": "datum.Alter == \"0-64\""}],
      "encoding": {
        "y": {
          "aggregate": "average",
          "field": "obeGrenze",
          "scale": {"domain": [0, 1800]},
          "type": "quantitative"
        },
        "y2": {
          "aggregate": "average",
          "field": "untGrenze"
        }
      }
    },
    {
      "mark": {
        "stroke":"#85A9C5", "type": "line", "interpolate": "monotone","point": true},
      "transform": [{"filter": "datum.Alter == \"0-64\""}],
      "encoding": {
        "y": {
          "aggregate": "mean",
          "field": "hochrechnung",
          "type": "quantitative",

          "axis": {}
        }
      }
    },
    {
      "mark": {
        "stroke": "#85A9C5", "type": "line", "interpolate": "monotone","point": ""},
      "transform": [{"filter": "datum.Alter == \"65\""}],
      "encoding": {
        "y": {
          "aggregate": "mean",
          "field": "hochrechnung",
          "type": "quantitative"
        }
      }
    },
    {
      "mark": "point",
      "transform": [{"filter": "datum.Alter == \"65\""}],
      "encoding": {
        "y": {
          "aggregate": "mean",
          "field": "hochrechnung",
          "type": "quantitative"
        },
        "tooltip": [{"field": "Woche", "type":"quantitative"},{"field": "hochrechnung", "type":"quantitative"}],
        "fill": { "value": "#fff" }
      }
    },
    {
      "mark": "point",
      "transform": [{"filter": "datum.Alter == \"0-64\""}],
      "encoding": {
        "y": {
          "aggregate": "mean",
          "field": "hochrechnung",
          "type": "quantitative"
        },
        "tooltip": [{"field": "Woche", "type":"quantitative"},{"field": "hochrechnung", "type":"quantitative"}],
        "fill": { "value": "#fff" }
      }
    }
  ]
}

我可以使用条件更改颜色，例如“test”：“datum['hocrechnung'] > 100”，但是当我尝试使用变量而不是数字时（例如“datum['obeGrenze']”，我不有什么影响。

我怎样才能做到这一点？

标签： vega-lite