{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "background": "white",
  "padding": 5,
  "height": 20,
  "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}
      ]
    }
  ],
  "signals": [
    {"name": "x_step", "value": 20},
    {
      "name": "width",
      "update": "bandspace(domain('x').length, 1, 0.5) * x_step"
    }
  ],
  "marks": [
    {
      "name": "marks",
      "type": "symbol",
      "style": ["point"],
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "transparent"},
          "stroke": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "point"},
          "description": {
            "signal": "\"a: \" + (isValid(datum[\"a\"]) ? datum[\"a\"] : \"\"+datum[\"a\"])"
          },
          "x": {"scale": "x", "field": "a"},
          "y": {"signal": "height", "mult": 0.5}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "point",
      "domain": {"data": "source_0", "field": "a", "sort": true},
      "range": {"step": {"signal": "x_step"}},
      "padding": 0.5
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "a",
      "labelAlign": "right",
      "labelAngle": 270,
      "labelBaseline": "middle",
      "zindex": 0
    }
  ]
}