choropleth map
A choropleth map visualizes global economic classifications by country, with each nation filled according to its assigned category from a ordinal color scale. Users can click legend entries to filter the map, highlighting matching countries while dimming others to 20% opacity; clicking the same legend entry again removes the filter. The map uses an SVG renderer with the d3-geo-projection Van Der Grinten IV projection, and employs d3-geoPath for path generation and d3.zoom for pan and zoom interactions. Data comes from the world-atlas TopoJSON dataset, merged with TSV metadata for country properties.