County Choropleth
A US county choropleth rendered as inline SVG from a caller-supplied TopoJSON, with theme diverging or sequential ramps, state borders, and a hover tooltip. Use it for print-quality county maps in articles; for zoomable, high-cardinality maps reach for the MapLibre engine instead.
County Choropleth
Installshow
viz add d3/geo/county-choropleth-v1Props
| Prop | Type | Description |
|---|---|---|
data | CountyChoroplethData | { topology (counties TopoJSON), counties: {fips, value, label?, sub?}[], domain?: [lo,mid,hi], unit?, title?, subtitle?, source? }. |
domain | number[] | Override the color domain. [lo, mid, hi] = diverging; [lo, hi] = sequential. |
See full TypeScript interface on GitHub for all props.
Usageshow
import CountyChoropleth from '@/viz/components/d3/geo/county-choropleth-v1';
Metadata
- FrameworkD3 / SVG
- CategoryMaps
- Source
d3/geo/county-choropleth-v1
Dependencies
Related Components
State bars
State-level bar charts for ranking US states on a single metric. Two implementations: a sortable Recharts version with search and expand affordances, and an Observable Plot version with built-in sorting. Both built around BRFSS state-level data but accept any 50-row state dataset.
Geographic Map
Choropleth maps in Observable Plot using the US Albers projection. The primary variant covers US states with built-in TopoJSON; alternates handle generic geographies (any TopoJSON or county-level resolution), European countries, and ZIP-code resolution. All variants are responsive to container width and accept standard TopoJSON / GeoJSON inputs.
County Choropleth (diverging)
The county choropleth tuned for residual / above-or-below maps: a diverging color scale centered on a reference value (the national mean or zero), so counties read as positive vs. negative at a glance. Same component as County Choropleth — just a centered three-stop domain. Derived from the diverging county maps across the birth_death + Politics data stories (e.g. two-despairs, merchant-right-county-residuals).
Bubble Map
Geographic bubble map with size-encoded values. Points positioned by lat/long, sized by a metric. Use when the data is point-located rather than region-aggregated — bubble maps avoid the "large area = more important" bias that choropleths can introduce when geographic regions vary dramatically in size.
Used in data stories
Live ctzn.pub articles built with this chart shape.
+2 more stories