This example shows the number of COVID-19 infection cases across Chinese provinces, stacked by transmission type (PublicTransit, Relative, Social, Unknown). Users can toggle between absolute counts and percentage-based views. The visualization uses d3.layout.stack and d3.svg.axis to render animated, stacked bar charts in SVG. A radio button triggers transitions between count and percent modes, while a custom tooltip and legend provide context. Data comes from a CSV file listing cases per province and transmission category.