{"version":"1.0","type":"rich","title":"Melting Data for Multiple Lines","description":"This visualization shows population over time by region, with multiple smoothed lines drawn from 1950 to 2100 using a basis curve. The code melts wide-format UN population data into tidy rows via a custom `melt` function, then uses `d3.nest()` to group by region and `d3.scaleOrdinal` with `schemeCategory10` for colors. A color legend, axis labels, and gridlines are rendered in SVG. Data merges two CSV sources for estimates and medium-variant projections.","provider_name":"VizHub AI Studio","provider_url":"https://vizhub.com","html":"<iframe src=\"https://vizhub.com/viz/8598513589044b6b89854a2d31141dee?mode=embed\" width=\"960\" height=\"500\" scrolling=\"no\" frameborder=\"0\"></iframe>","width":960,"height":500,"cache_age":3600}