This example visualizes a smoothed radar chart comparing passenger ratings across multiple French train stations, showing metrics like cleanliness, security, and communication. The D3.js v4 code loads station data from a CSV file using `d3.csv`, then renders the chart as an SVG with two station profiles overlaid. It uses a custom `RadarChart` function that draws circular grid lines, labels, and area polygons with optional glow filters, animated to display the comparative data.