htl.html`${d3
.sort(
d3.groups(data, (d) => d.group),
(d) => d[0]
)
.map(([groupNum, groupData]) =>
Plot.plot({
marginLeft: 100,
x: { grid: true, domain: xDomain },
y: { label: `letter (group ${groupNum})` },
marks: [
Plot.barX(groupData, { y: "letter", x: "frequency", sort: { y: "-x" } })
]
})
)}`