spec = ({
marginLeft: 120,
marginRight: 90,
grid: true,
color: { type: "ordinal", scheme: "category10", legend: true },
x: { nice: true, grid: true },
y: { grid: true },
facet: { data, y: "site", marginRight: 90 },
marks: [Plot.dot(data, { x: "yield", y: "variety", fill: "year" })]
})