Bar chart with highlighting on hover and selection on click

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Vega-Lite JSON Specification

{
  "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
  "description": "A bar chart with highlighting on hover and selecting on click. (Inspired by Tableau's interaction style.)",
  "data": {
    "values": [
      {"a": "A","b": 28}, {"a": "B","b": 55}, {"a": "C","b": 43},
      {"a": "D","b": 91}, {"a": "E","b": 81}, {"a": "F","b": 53},
      {"a": "G","b": 19}, {"a": "H","b": 87}, {"a": "I","b": 52}
    ]
  },
  "selection": {
    "highlight": {"type": "single", "empty": "none", "on": "mouseover"},
    "select": {"type": "multi"}
  },
  "mark": {
    "type": "bar",
    "fill": "#4C78A8",
    "stroke": "black",
    "cursor": "pointer"
  },
  "encoding": {
    "x": {"field": "a", "type": "ordinal"},
    "y": {"field": "b", "type": "quantitative"},
    "fillOpacity": {
      "condition": {"selection": "select", "value": 1},
      "value": 0.3
    },
    "strokeWidth": {
      "condition": [
        {
          "test": {
            "and": [
              {"selection": "select"},
              "length(data(\"select_store\"))"
            ]
          },
          "value": 2
        },
        {"selection": "highlight", "value": 1}
      ],
      "value": 0
    }
  },
  "config": {
    "scale": {
      "bandPaddingInner": 0.2
    }
  }
}