This example demonstrates how to compute and display the average sepal length for each iris species using D3. It loads data from a CSV file via a fetch request and parses it with the `csvParse` API. The visualization uses D3's `flatRollup` and `sum` functions to aggregate the data, then renders the resulting summary as a JSON string in a `<pre>` element. The code demonstrates loading D3 from UNPKG and using local ES6 modules.