This example demonstrates real-time animated data joins in a browser window. It uses D3’s `select` API to create an SVG canvas and repeatedly updates a dataset of circles via `setInterval`. The code explicitly exercises the `.join('circle')` method to bind new data to existing SVG circle elements, transitioning their `cx`, `cy`, and `r` attributes based on a sine wave function. The visualization shows smooth, continuous motion of circles while also varying their count (from 5 to 15) over time, all rendered as vector shapes. D3’s `range` utility generates the underlying numeric sequence for the dataset.