This example shows how D3.js can animate transitions between two different datasets, displayed as orange circles along a horizontal axis. The circles’ radii and horizontal spacing are derived from each dataset’s values, and a button toggles between the two arrays. The implementation uses `transition()` to animate the circles’ `cx`, `cy`, and `r` attributes over 500 milliseconds. The code relies on D3’s selection and `.enter()`/`.exit()` methods to add or remove circles when the dataset changes, with SVG elements for rendering.