geom-density-2d
2D density layer: contour lines of the estimated (x, y) density.
Mapping must provide x and y; the layer accepts raw observations, no pre-computed grid is needed. Map colour to after-stat("_level") to shade the lines by density level.
Usage
geom-density-2d(
mapping: none,
data: none,
bw: auto,
adjust: 1,
n: 25,
bins: 10,
binwidth: none,
breaks: auto,
stroke: auto,
colour: auto,
alpha: auto,
linetype: auto,
stat: auto,
position: "identity",
key: auto,
inherit-aes: true,
)Parameters
| Parameter | Default | Description |
|---|---|---|
mapping |
none |
Layer-specific aesthetic mapping built with aes. Must map x and y. |
data |
none |
Layer-specific dataset, or a function applied to the plot data returning the layer frame. Falls back to the plot data when none. |
bw |
auto |
Kernel standard deviation per axis. auto derives it per axis from R’s bw.nrd / 4; pass a number for both axes or an (x, y) tuple. |
adjust |
1 |
Bandwidth multiplier: adjust: 0.5 halves the smoothing. |
n |
25 |
Density grid resolution per axis: a number or an (x, y) tuple. |
bins |
10 |
Target contour-level count when breaks and binwidth are unset. |
binwidth |
none |
Fixed step between levels. Overrides bins. |
breaks |
auto |
Explicit array of contour levels. Overrides bins and binwidth. |
stroke |
auto |
Line thickness (a Typst length). |
colour |
auto |
Fixed line colour. auto resolves via the colour scale. |
alpha |
auto |
Line opacity in [0, 1]. |
linetype |
auto |
Dash keyword. auto honours the linetype scale. |
stat |
auto |
Statistical transform. auto builds stat-density-2d from the parameters above; pass a stat name or stat object to override. |
position |
"identity" |
Position adjustment name. Usually "identity". |
key |
auto |
Legend glyph override built with a draw-key-* helper. auto picks the default for the geom. |
inherit-aes |
true |
Whether to merge the plot-level mapping into this layer’s mapping. |
Returns
Layer dictionary consumed by plot.
Examples
Density contours around 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-point(size: 1.5pt, alpha: 0.5),
geom-density-2d(),
),
width: 10cm,
height: 6cm,
)
