This example demonstrates a dynamic scatterplot where fifteen circles move in a sine wave pattern, updating at 60 frames per second. It shows how D3's selection API can manage elements declaratively, using the `select` and `range` functions from the D3 library. The code constructs an SVG canvas, generates new data points each frame, and applies them to the circles using the `.data()` and `.join()` methods, which handle updating and entering elements. The animation runs in a browser window, with the circles’ positions calculated from a mathematical sine function.