geom-hline
Horizontal reference line at one or more y intercepts.
yintercept can be a scalar or an array drawing one line per value. To drive the lines from data instead, bind yintercept (and optionally colour, alpha, linewidth, linetype) through aes and pass data; one line is then drawn per row, with aesthetics resolved per row.
Usage
geom-hline(
mapping: none,
data: none,
yintercept: none,
colour: auto,
stroke: auto,
alpha: auto,
linetype: auto,
inherit-aes: false,
)Parameters
| Parameter | Default | Description |
|---|---|---|
mapping |
none |
Aesthetic mapping built with aes. Bind yintercept to a column to draw a data-driven line per row. |
data |
none |
Layer-specific dataset for the mapped yintercept column, or none. |
yintercept |
none |
Scalar or array of y values at which to draw horizontal lines, used when yintercept is not mapped. Values may be numeric or ISO-8601 date/datetime/time strings when a temporal y scale is active. |
colour |
auto |
Line colour. auto inherits the theme ink. |
stroke |
auto |
Line thickness (a Typst length). |
alpha |
auto |
Line opacity in [0, 1]. |
linetype |
auto |
Dash keyword. Defaults to "solid". |
inherit-aes |
false |
Whether to merge the plot-level mapping into this layer’s mapping. Defaults to false. |
Returns
Layer dictionary consumed by plot.
Examples
Single horizontal reference line at y = 5.
#let d = range(0, 10).map(i => (x: i, y: i + 2))
#plot(
data: d,
mapping: aes(x: "x", y: "y"),
layers: (
geom-point(size: 2pt),
geom-hline(yintercept: 5, colour: rgb("#cc0000")),
),
width: 10cm,
height: 6cm,
)
Pass an array of intercepts to draw several reference lines at once.
#let d = range(0, 10).map(i => (x: i, y: i + 2))
#plot(
data: d,
mapping: aes(x: "x", y: "y"),
layers: (
geom-point(size: 2pt),
geom-hline(yintercept: (3, 6, 9), colour: rgb("#888888")),
),
width: 10cm,
height: 6cm,
)
Drive reference lines from data: bind yintercept and colour through aes so each threshold row draws its own coloured line.
#let d = range(0, 10).map(i => (x: i, y: i + 2))
#let thresholds = ((at: 4, lvl: "low"), (at: 8, lvl: "high"))
#plot(
data: d,
mapping: aes(x: "x", y: "y"),
layers: (
geom-point(size: 2pt),
geom-hline(mapping: aes(yintercept: "at", colour: "lvl"), data: thresholds),
),
width: 10cm,
height: 6cm,
)
