Stacked area chart

This example shows how related series can be compounded into a stacked area chart using fill-between.

#let stacked-area(x, ..y) = {
  y
    .pos()
    .fold(
      ((0,) * x.len(),) , (ys-stacked, ys) => {
        let previous = ys-stacked.last()
        ys-stacked.push(lq.vec.add(previous, ys))
        ys-stacked
      }
    )
    .windows(2)
    .map(((y1, y2)) => lq.fill-between(x, y1, y2: y2))
}

#let x = range(10)
#let y1= (0, 1, 3, 9, 5, 4, 2, 2, 1, 0)
#let y2 = (5, 3, 2, 0, 1, 2, 2, 2, 3, 2)
#let y3 = (0, 0, 0, 0, 1, 2, 4, 5, 5, 9)

#lq.diagram(
  ..stacked-area(x, y1, y2, y3)
)

Stacked area charts are useful for showing the relationship between categories of the same type in one chart, but beware that including too many series can harm readability.