This D3.js scatter plot visualizes the Iris dataset, encoding petal length and petal width along the x- and y-axes while coloring each point by species (setosa, versicolor, virginica) using a custom marker function. The chart uses `d3.csv` to load the external iris.csv file, `d3.scaleLinear` for axes, and `d3.axisLeft`/`d3.axisBottom` for ticks. Each circle is rendered via SVG, with sepal measurements additionally stored as data attributes, and the plot adapts to the full browser window.