CHOROPLETH

supplied region polygons filled by a deterministic value ramp. Needs: region polygons (author-supplied geometry) + one value per region.

magnitudepattern

DL-01 AGRAW

Use when

rates and intensities across known territories
where-is-it-worst questions for map-literate audiences

Do not use when

absolute counts (big areas lie; CH-SPA-02)
territories the audience cannot recognize

See instead

geography adds nothing to the message: CH-RNK-01
absolute counts, not rates: CH-SPA-02

Alternatives

CH-RNK-01 (values without geography)
CH-SPA-02 (absolute counts)

Rules

fill is the deterministic background-to-high ramp; the value key is printed
every region labeled with name and value on the map
geometry is data: the same polygons re-render identically forever

Never do this

rainbow choropleths
absolute counts on area fills
unlabeled regions
3D extrusion

QA before delivering

ramp key printed
values on the map
polygons closed
source present

Data shape

title	action title with a number
source	bottom-left always
unit	on first region value
note	coordinates are author-supplied unit-square (0-100) geometry; the renderer scales, the author owns projection and aspect
regions	[{name, polygon: [[x,y]..], label_at: [x,y], value}]

Sample data (golden)

{
  "title": "Central region holds 58 of 170 open items",
  "eyebrow": "OPEN ITEMS BY REGION",
  "source": "Source: sample dataset v1, 2026-07-12",
  "unit": "items",
  "regions": [
    {
      "name": "North",
      "label_at": [
        32,
        17
      ],
      "polygon": [
        [
          10,
          5
        ],
        [
          55,
          2
        ],
        [
          60,
          25
        ],
        [
          35,
          32
        ],
        [
          8,
          28
        ]
      ],
      "value": 12
    },
    {
      "name": "West",
      "label_at": [
        19,
        45
      ],
      "polygon": [
        [
          8,
          28
        ],
        [
          35,
          32
        ],
        [
          30,
          60
        ],
        [
          5,
          58
        ]
      ],
      "value": 34
    },
    {
      "name": "Central",
      "label_at": [
        48,
        42
      ],
      "polygon": [
        [
          35,
          32
        ],
        [
          60,
          25
        ],
        [
          68,
          50
        ],
        [
          30,
          60
        ]
      ],
      "value": 58
    },
    {
      "name": "East",
      "label_at": [
        78,
        38
      ],
      "polygon": [
        [
          60,
          25
        ],
        [
          92,
          20
        ],
        [
          95,
          55
        ],
        [
          68,
          50
        ]
      ],
      "value": 21
    },
    {
      "name": "South",
      "label_at": [
        58,
        72
      ],
      "polygon": [
        [
          30,
          60
        ],
        [
          68,
          50
        ],
        [
          95,
          55
        ],
        [
          90,
          90
        ],
        [
          25,
          88
        ]
      ],
      "value": 45
    }
  ]
}