This example visualizes the classic Iris dataset as a scatterplot, with sepal length and width mapped to the x and y axes, petal length encoded by point size, and petal width by color. Built with D3 v4 and rendered as SVG, the chart separates the three species (setosa, versicolor, virginica) using distinct colors, and includes axes, a legend, and transition-based brushing that filters points based on a selection. The visualization is a work in progress, forked from an earlier block, and uses the famous Fisher iris measurements from the bundled `data.csv`.