This example shows a Sankey diagram of car evaluation data, displaying proportional relationships between attributes like buying price, maintenance cost, doors, persons, luggage boot, and safety. The diagram uses a React-based D3 v4 implementation with the custom `d3.sankey` layout, where nodes can be dragged vertically within their columns to explore connections. The code reads a CSV dataset from a remote URL, calculates ratio-based link values between attribute pairs, and renders the visualization as an SVG with draggable nodes and hover tooltips showing node names and values.