This example shows a line chart of revenue aggregated by product category from a CSV dataset. D3.js (v7) loads the data, rolls up categories, and sums their revenue. It renders an SVG with axes, a steelblue polyline, and orange data points. The code uses `d3.scalePoint`, `d3.scaleLinear`, `d3.axisBottom`, `d3.axisLeft`, and `d3.line` to draw the visualization.