This example shows a scatter plot of the Iris flower dataset, mapping sepal length on the x-axis and petal length on the y-axis, with circles colored by a fixed opacity. The visualization is built using React and D3 v7, where React manages the component lifecycle and the `d3.select` API handles SVG rendering. Data is loaded via `d3.csv` and parsed into numeric fields, while scales are created with `d3.scaleLinear` and axes are appended using `d3.axisLeft` and `d3.axisBottom`. The code demonstrates a decoupled pattern for integrating D3 within a React application.