Pie Chart (Vega)

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A simple pie chart with embedded data.",
  "width": 400,
  "height": 400,
  "autosize": "none",

  "data": [
    {
      "name": "table",
      "values": [
        {"category": "A", "amount": 28},
        {"category": "B", "amount": 55},
        {"category": "C", "amount": 43},
        {"category": "D", "amount": 91},
        {"category": "E", "amount": 81},
        {"category": "F", "amount": 53},
        {"category": "G", "amount": 19},
        {"category": "H", "amount": 87}
      ],
      "transform": [
        {
          "type": "pie",
          "field": "amount"
        }
      ]
    }
  ],

  "scales": [
    {
      "name": "color",
      "type": "ordinal",
      "domain": {"data": "table", "field": "category"},
      "range": {"scheme": "category20"}
    }
  ],

  "marks": [
    {
      "type": "arc",
      "from": {"data": "table"},
      "encode": {
        "enter": {
          "fill": {"scale": "color", "field": "category"},
          "x": {"signal": "width / 2"},
          "y": {"signal": "height / 2"},
          "startAngle": {"field": "startAngle"},
          "endAngle": {"field": "endAngle"},
          "innerRadius": {"value": 0},
          "outerRadius": {"signal": "width / 2"}
        }
      }
    }
  ]
}