A React and D3 scatter plot visualizes hospital readmission metrics across U.S. states, comparing the number of hospitals performing worse versus better than the national average for each measure. The code loads CSV data, converts non-numeric values to NaN, and filters out invalid points before rendering circles with d3.scaleLinear. The `viz` function uses `selectAll` and `data().join()` to bind points, with padding applied to the x and y axes. The dataset comes from CMS hospital readmission rates per state.