This example shows a radial pie chart of US state population data across age groups. The chart uses a circular layout with stacked bars for each state, and labels for state abbreviations positioned around the outer ring. The code leverages `d3.scaleBand` for angular positioning, `d3.scaleRadial` from the `d3-scale-radial` library for radii, and `d3.stack` for the stacked segments. SVG paths are drawn using `d3.arc`, with color encoding via `d3.scaleOrdinal` and a legend for age categories.