{
  "$schema": "urn:prism:schema:v1:spec",
  "title": "Region x bucket heatmap",
  "data": {
    "name": "matrix",
    "values": [
      {"region": "NA", "bucket": "0-25", "count": 10},
      {"region": "NA", "bucket": "26-50", "count": 18},
      {"region": "EU", "bucket": "0-25", "count": 7},
      {"region": "EU", "bucket": "26-50", "count": 22}
    ]
  },
  "mark": "heatmap",
  "encoding": {
    "x":     {"field": "region", "type": "nominal"},
    "y":     {"field": "bucket", "type": "ordinal"},
    "color": {"field": "count",  "type": "quantitative"}
  }
}