This example uses React and D3 to load a CSV of Velib bike-sharing data and aggregate it by hour using `d3.rollups` with a sum of `num_bikes_available`. It then renders a scatter plot of circles with positions and opacity randomized on each render, sized by the summed bike counts. The SVG dimensions are 960×500, and the data pulls from a GitHub-hosted CSV. The app shows a loading message until the CSV parses asynchronously via `d3.csv`, after which it maps each group to a circle.