Sized Points on a Map
This example renders a world map with circles sized by population for cities over 50,000 inhabitants, using a square-root scale to encode the data. The map is drawn with React and SVG, projecting geographic coordinates through D3’s `geoNaturalEarth1` and `geoPath`, with graticules and country boundaries from the World Atlas TopoJSON. City data comes from Simplemaps, and each point’s radius is determined by `scaleSqrt` mapping maximum population to a 15-pixel radius.