This example demonstrates the results of applying D3 data-transformation APIs to a dataset of Human Development Index (HDI) indicators for countries across multiple years. It shows how aggregation methods like `flatRollup`, grouping via `flatGroup`, and `bin` summarize and reshape the raw CSV data into compact summaries. The visualization outputs the transformed results as formatted JSON text using `select` and `join`, displaying counts, averages, or binned ranges depending on the uncommented transformation. The code relies on D3 v7 functions such as `csvParse`, `bin`, `min`, `max`, and `extent` to process the data.