Let's make a bar chart with D3.js!
A bar chart maps country populations from a CSV file to horizontal rectangles. The chart uses D3 v5’s `scaleLinear` and `scaleBand` to position and size bars, with population values multiplied by 1,000 and rendered as SVG `rect` elements. Data loading relies on `d3.csv`, and the layout is fixed at 960 by 500 pixels. The example focuses on the fundamental steps of binding data to SVG shapes and encoding values through a linear scale.