Projected Choropleth

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Projected Choropleth

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Last edited Feb 9, 2016

Created on Jul 4, 2013

A choropleth map shows unemployment rates by U.S. county, using a blue sequential color scale with nine quantized classes for rates from 0 to 15 percent. State boundaries appear as white lines, while counties are drawn as SVG paths. The map uses pre-projected TopoJSON data, created via the `topojson` command-line tool with the `d3.geo.albersUsa()` projection, and renders using `d3.geo.path()`. County geometries and unemployment rates are joined into a single file during preprocessing, eliminating separate data loads. This variation of the classic unemployment choropleth simplifies the workflow by embedding the projection and data join directly into the TopoJSON generation step.

AI-generated description

This variation of the unemployment choropleth uses topojson --projection to create projected TopoJSON with the d3.geo.albersUsa projection.

This example also uses the -e argument to join the county geometries with a TSV file of unemployment rates, simplifying the implementation and eliminating the need to load multiple data files.

gpl-3.0 Licensed

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