A bar chart showing the frequency of letters in a dataset, rendered with React and D3 v7. The visualization displays interactive bars that respond to clicks, highlighting the selected category while dimming others. The code combines React's `useState` hook for state management with D3's `scaleBand`, `scaleLinear`, and axis components, using a `ResizeObserver` to handle responsive resizing. Data loads from a local CSV file, and bars apply transitions on hover and selection.