This example visualizes the Iris dataset as an interactive scatter plot, allowing users to select which quantitative columns appear on the X and Y axes via two dropdown menus. The chart updates dynamically, with each point colored by the iris species (setosa, versicolor, or virginica) and axis labels reflecting the chosen variables. The visualization uses D3 v5 APIs such as `d3.scaleLinear`, `d3.axisLeft`, `d3.axisBottom`, and `d3.extent` to build the axes and scales, while data is loaded from a CSV file using `d3.csv`.