This scatter plot matrix compares weekly U.S. gasoline prices across four fuel grades—All Grades, Regular, Midgrade, and Diesel—from early 1995 onward. Each cell displays a scatter of points, with tooltips revealing the specific week and price values on hover. Built with D3 v7, the visualization uses `d3.csv` to load the data, `d3.scaleLinear` for axes, and `d3.axisBottom`/`d3.axisLeft` for tick marks. The SVG-based rendering includes a cross-product helper to generate all pairwise combinations of the selected columns.