An animated scatterplot cycles through four Iris flower measurements, updating the x-axis every 3.5 seconds while keeping sepal length on the y-axis. D3 version 7 renders SVG symbols whose size reflects petal width and whose color and shape encode species. The reusable `scatterplot` function uses `scaleLinear`, `scaleSqrt`, `scaleOrdinal`, and `transition` to animate axis changes and point movement, loading data from a CSV via `d3.csv`.