This scatter plot visualizes the Iris dataset with SVG circles representing flowers, animated via `transition()`. A reusable chart function built with D3 v6 scales axes using `scaleLinear` and `extent`, rendering axes with `axisLeft` and `axisBottom`. Clicking the button cycles the x-axis variable among petal width, sepal width, petal length, and sepal length, updating the plot idempotently through `selection.call()`. Data loads from a remote CSV, with parsing for numeric values.