A tree diagram visualizes the distribution of cardiovascular disease risk factors among patients, branching from overall risk into cholesterol, glucose, and smoking categories, then into outcome counts for cardiovascular disease presence or absence. Leaf nodes display patient counts with tooltips providing detailed breakdowns. The visualization is rendered using D3.js v7 with the `d3.hierarchy` and `d3.tree` layouts, drawing SVG links and circles for nodes. Styling applies gray links and black node strokes to clarify the hierarchical structure.