This example creates a scatter plot matrix (SPLOM) of the classic Iris flower dataset, showing pairwise relationships between sepal length, sepal width, petal length, and petal width, with points colored by species. Brushing a rectangular region in any cell highlights the selected points across all other cells, dimming unselected points to reveal correlations between different variable pairs. Built with D3.js v3, the visualization uses `d3.svg.brush` for the interactive selection, `d3.scale.linear` for axes, and `d3.svg.axis` for tick marks, rendering all elements as SVG.