This example shows yearly profit as blue bars on a left axis and the average unit price as a red line on a right axis, using data loaded from a CSV via `d3.csv`. It computes yearly aggregates with `d3.rollup` and `d3.sum`. The visualization renders with `d3.select` and `append` into an SVG, using `d3.scaleBand` and `d3.scaleLinear` for the axes, and draws the line with `d3.line`.