Auto Updating Bar Graph
This example shows a grouped bar chart comparing success and failure counts for several people. The animated visualization periodically toggles between showing data for all five people and a slightly smaller dataset, causing the bars to transition as the underlying data changes. Built with D3 v4, the code uses `d3.scaleBand`, `d3.scaleLinear`, and `d3.scaleOrdinal` for scales and color, while `d3.tip` provides hover tooltips. The graph renders as SVG and updates by removing the old chart and re-appending new elements inside a timed loop that alternates between two JSON data files.