This visualization displays the average sepal length for each iris species using D3 v7. The code loads iris data from a CSV file, parses it with `d3.csvParse`, and aggregates measurements using `d3.flatRollup` and `d3.sum`. Results are rendered as formatted JSON text displayed in a `<pre>` element. The example demonstrates a data transformation pipeline, starting with raw tabular data and summarizing it through grouping and reduction operations.