Threshold Choropleth
A Threshold Choropleth displays US county unemployment rates quantized into color bands. The map uses a threshold scale to map continuous rate values, ranging from two to ten percent, into discrete shades of purple. `d3.scale.threshold()` defines the domain boundaries and corresponding range colors. The visualization renders SVG paths for counties, colored via `style("fill")`, with state borders overlaid. Data is loaded from a TSV file containing county IDs and rates, and geospatial shapes come from a TopoJSON file processed with `topojson.feature` and `d3.geo.path()`.
AI-generated descriptionThis choropleth uses a threshold scale for quantization, mapping arbitrary slices of a continuous domain to discrete values in the range. Unemployment rates ranging from 2 to 10% are quantized into different shades of purple.
var color = d3.scale.threshold()
.domain([0.02, 0.04, 0.06, 0.08, 0.10])
.range(["#f2f0f7", "#dadaeb", "#bcbddc", "#9e9ac8", "#756bb1", "#54278f"]);