This visualization displays a topic model’s data as a vertical column of small purple squares, with each square’s opacity reflecting the value in the second data column. It reads data from a remote CSV file via `d3.csv`, then renders the first 2,000 records as an SVG using `selectAll('rect')` and `insert('rect')`. Each rectangle is positioned 10 pixels apart, with fixed width and height of 8 pixels. The example uses D3 v5 and demonstrates a simple, minimal approach to encoding quantitative values through opacity.