This example animates a dynamic set of circles whose positions and radii oscillate over time. The visualization updates 100 times per second, using a sine wave to vary the number of circles between 1 and 19, while each circle’s y-coordinate and radius also fluctuate based on its index and time. The code uses D3’s `select` and `range` functions to build an SVG scene, with the `vizData` function applying a `join` operation to smoothly update circle attributes. Data is generated on the fly by the `makeData` function using trigonometric calculations, with no external data source.