This example visualizes the Iris Dataset with a scatter plot of sepal length against petal length, coloring each point by species. An interactive color legend lists the three species; hovering over a legend entry highlights the corresponding marks by adjusting their opacity, while dimming the rest. The chart uses D3 v7 APIs including `scaleOrdinal`, `schemeCategory10`, `selection.join`, and event handlers for mouseover and mouseout. Data is loaded asynchronously from a CSV and parsed with `csvParse`.