stat-density-2d-filled

Filled 2D density statistic: iso-bands of a Gaussian kernel density estimate.

Smooths the (x, y) sample into a density surface on an n × n grid, then cuts the surface into level bands. Emits the same row shape as stat-contour-filled (closed polygons with fill bound to _level), so it pairs with geom-density-2d-filled or geom-polygon.

Either breaks, binwidth, or bins controls band placement; precedence runs breaks > binwidth > bins (default bins: 10).

from R’s bw.nrd / 4 (the seed MASS kde2d uses); pass a number for both axes or an (x, y) tuple.

Usage

stat-density-2d-filled(
  bw: auto,
  adjust: 1,
  n: 25,
  bins: 10,
  binwidth: none,
  breaks: auto,
)

Parameters

Parameter	Default	Description
bw	auto	Kernel standard deviation per axis. auto derives it per axis
adjust	1	Bandwidth multiplier: adjust: 0.5 halves the smoothing.
n	25	Grid resolution per axis: a number or an (x, y) tuple.
bins	10	Target band count when breaks and binwidth are unset.
binwidth	none	Fixed step between band edges. Overrides bins.
breaks	auto	Explicit array of band edges. Overrides bins and binwidth.

Returns

Statistic object with name: "density-2d-filled".

Outputs

• x.
• y.
• group.
• _level.

Examples

Shaded density bands of two point clouds.

#let d = range(0, 60).map(i => {
  let lobe = calc.rem(i, 2)
  (
    x: 2 + lobe * 4 + calc.sin(i * 1.7) * 0.8,
    y: 2 + lobe * 3 + calc.cos(i * 2.3) * 0.8,
  )
})
#plot(
  data: d,
  mapping: aes(x: "x", y: "y"),
  layers: (geom-density-2d-filled(bins: 8),),
  scales: scales(
    x: scale-continuous(expand: (0, 0)),
    y: scale-continuous(expand: (0, 0)),
  ),
  width: 10cm,
  height: 6cm,
)

See also

geom-density-2d-filled, stat-contour-filled, stat-density-2d.