Plot.plot({
marks: [
Plot.ruleX(["A"], { strokeWidth: 2, stroke: "green" }),
Plot.ruleX([0], { strokeWidth: 2, stroke: "blue" }),
Plot.ruleY([0], { strokeWidth: 2, stroke: "red" }),
Plot.barY(alphabet, {x: "letter", y: "frequency", sort: {x: "y2"}})
]
})