{
  "$schema": "urn:prism:schema:v1:spec",
  "title": "Traffic source share",
  "data": {
    "values": [
      {"source": "organic", "visits": 4120},
      {"source": "paid",    "visits": 2080},
      {"source": "social",  "visits": 1530},
      {"source": "email",   "visits": 870},
      {"source": "direct",  "visits": 1290}
    ]
  },
  "mark": "donut",
  "encoding": {
    "theta": {"field": "visits", "type": "quantitative"},
    "color": {"field": "source", "type": "nominal"}
  }
}