This example visualizes the absolute frequencies of categorical data columns ("note" and "student") as a bar chart. A dropdown menu selects which column to display, and each bar shows the count alongside a tooltip on hover, with highlighted bars displaying divergence annotations. Built with React and D3 v5, it uses `d3.nest()` for data aggregation, `scaleBand` and `scaleLinear` for scales, and `axisBottom`/`axisLeft` for axes. SVG rendering includes animated hover effects and mouse event handlers for interactivity.