{"version":"1.0","type":"rich","title":"Untitled","description":"A choropleth map of population density per square mile colors U.S. census block groups using a threshold scale and the sequential color scheme `d3.schemeOrRd[9]`. The visualization includes a square-root-scaled legend with an axis, and overlays county boundaries as black strokes at 30% opacity. The code loads TopoJSON data via `d3.json`, converts it with `topojson.feature`, and renders it with `d3.geoPath`. The legend uses `d3.scaleThreshold` and `d3.axisBottom`. The map is built with D3 v4 and React in the supporting files.","provider_name":"VizHub AI Studio","provider_url":"https://vizhub.com","html":"<iframe src=\"https://vizhub.com/viz/a3d202f29e924a5f9bc3797cdfca2c1a?mode=embed\" width=\"960\" height=\"500\" scrolling=\"no\" frameborder=\"0\"></iframe>","width":960,"height":500,"cache_age":3600}