{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "background": "white",
  "padding": 5,
  "width": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"a": "C", "b": 2},
        {"a": "C", "b": 7},
        {"a": "C", "b": 4},
        {"a": "D", "b": 1},
        {"a": "D", "b": 2},
        {"a": "D", "b": 6},
        {"a": "E", "b": 8},
        {"a": "E", "b": 4},
        {"a": "E", "b": 7}
      ]
    },
    {
      "name": "data_0",
      "source": "source_0",
      "transform": [
        {
          "type": "aggregate",
          "groupby": ["a"],
          "ops": ["average"],
          "fields": ["b"],
          "as": ["average_b"]
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"average_b\"]) && isFinite(+datum[\"average_b\"])"
        }
      ]
    }
  ],
  "signals": [
    {"name": "y_step", "value": 20},
    {
      "name": "height",
      "update": "bandspace(domain('y').length, 0.1, 0.05) * y_step"
    }
  ],
  "marks": [
    {
      "name": "marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"Average of b: \" + (format(datum[\"average_b\"], \"\")) + \"; a: \" + (isValid(datum[\"a\"]) ? datum[\"a\"] : \"\"+datum[\"a\"])"
          },
          "x": {"scale": "x", "field": "average_b"},
          "x2": {"scale": "x", "value": 0},
          "y": {"scale": "y", "field": "a"},
          "height": {"scale": "y", "band": 1}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "linear",
      "domain": {"data": "data_0", "field": "average_b"},
      "range": [0, {"signal": "width"}],
      "nice": true,
      "zero": true
    },
    {
      "name": "y",
      "type": "band",
      "domain": {"data": "data_0", "field": "a", "sort": true},
      "range": {"step": {"signal": "y_step"}},
      "paddingInner": 0.1,
      "paddingOuter": 0.05
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "gridScale": "y",
      "grid": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "Average of b",
      "labelFlush": true,
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(width/40)"},
      "zindex": 0
    },
    {"scale": "y", "orient": "left", "grid": false, "title": "a", "zindex": 0}
  ]
}