This example displays a text-based summary of the Iris dataset, showing the average sepal length for each of the three species. Using D3 v7’s `flatRollup` and `sum` functions, it computes the mean values and renders them as JSON in a `<pre>` element. The data is loaded asynchronously via `fetch` and parsed with `csvParse`, with numeric fields coerced to numbers before aggregation. The visualization updates through a state management pattern where `setState` triggers a re-render.