Nested Donut Chart Example
This example uses a hierarchical dataset of topics and subtopics to render a multi-level nested donut chart in SVG. The D3.js partition layout arranges arcs for each layer, with custom radius adjustments in the arc generator distinguishing depth levels; the outer month wheel uses a separate pie layout. Color fills vary per parent topic, while click handlers on each arc display names, and labels are positioned through a custom transform function.