This example demonstrates an interactive transition between stacked and grouped bar charts, using sequenced animations to preserve object constancy as the data morphs between the two views. A radio button form toggles the mode, while D3 v4 APIs like `d3.scaleBand`, `d3.scaleLinear`, and `d3.stack` handle the layout and stacking. The transitions use `rect.transition()` with staggered delays and duration to smoothly animate each rectangle’s x-position, width, y-position, and height. The visualization renders with SVG, inspired by Heer and Robertson’s animated transition techniques.