This example demonstrates how to transform and summarize the Iris dataset using D3’s `flatRollup` and `sum` APIs. It first loads a CSV file asynchronously, parses it with `csvParse`, and converts numeric fields from strings to numbers. The visualization then computes the average sepal length per species and displays the resulting summary as formatted JSON in a `<pre>` element. The code also illustrates local ES6 module imports and state management through a simple `setState` pattern.