This example plots the classic Iris flower dataset on a scatterplot, using sepal length and petal length as the x- and y-axes. Species are distinguished by different symbol shapes, with a legend that supports interactive filtering by clicking on a species. The visualization is built with D3 v7, using `d3.scaleLinear`, `d3.scaleOrdinal`, and `d3.symbol` for shape encoding. Data loads from a CSV file, and hover interactions update the legend’s opacity to highlight the selected species.