都道府県マップ
A choropleth map of Japanese prefectures visualizes the birthplaces of Western-style painters from the Meiji era. Each prefecture is colored according to the number of painters born in a selected year, with a legend mapping values to a white-cyan-red gradient. Users click year labels to update the map's fill colors, with a zoom behavior for navigation. The visualization uses the d3.v3 library, d3.geo.path with a Mercator projection, and reads prefectural border data from 'japan.topojson' and painter data from 'meiji_gaka.csv'. Hovering over a prefecture displays a tooltip with the prefecture name, painter count, and their names.