A 4×4 scatter plot matrix compares every pair of numeric fields in the iris dataset, with circles colored by species using a d3.scaleOrdinal and the schemeSet1 color array. Each cell combines d3.axisLeft and d3.axisBottom for scales, while d3.csv loads the data from a Gist. The SVG charts are sized to a quarter of the window, and titles appear only on the diagonal cells. The code relies on vanilla JavaScript with d3 v6, using d3.select, d3.extent, and d3.scaleLinear per plot.