This example shows a scatter plot of Iris flower measurements, using sepal length on the x-axis and petal length on the y-axis, with a legend encoding species via different symbol shapes. The visualization loads data from a CSV file and renders it as D3 symbols, using `d3.scaleLinear` for axes, `d3.scaleOrdinal` for shape mapping, and `d3.axisLeft`/`d3.axisBottom` for ticks. A custom legend is drawn with reusable D3 selections, while the plot updates dynamically through a state-based render loop.