This example shows a simple bar chart of letter frequencies from a small CSV dataset. The chart uses a React component with hooks and a ResizeObserver for responsive dimensions. D3’s scaleBand and scaleLinear create the scales, while axisBottom and axisLeft render axes with gridlines. Clicking a bar toggles a selected state, changing its fill and opacity through transitions. The code integrates D3 selections with React state management, using modular rendering functions for the SVG, title, bars, and data loading.