A brushable scatter plot matrix of the classic Iris flower dataset, rendered in SVG with D3 v7. The four measured features are paired across all combinations, showing categorical color-coded points for the three species. Brushing a region in any scatter plot filters the data across the entire matrix, updating the diagonal histograms to reflect the selected subset with species-specific stacked colors. The visualization uses `d3.scalePoint`, `d3.scaleLinear`, and `d3.brush` to coordinate interactions.