A punchcard chart displays barley yield data across six sites, with each row representing a barley genotype and each column a year. Users select a site from a dropdown menu to trigger a smooth, 750-millisecond transition that updates the chart via the D3.js **v4** general update pattern. The visualization uses **d3.scalePoint** for axes, **d3.scaleSqrt** for circle radii, **d3.scaleOrdinal** with **d3.schemeCategory20b** for colors, and **d3.axisLeft**/ **d3.axisBottom** for rendering. Data from `barleyfull.csv` is loaded using **d3.csv** and processed with **d3.nest** and **d3.map**, with events handled via **d3.dispatch**.