mark_polygon: Add a polygon mark

In glyph: A Grammar of Interactive Graphics

Add a polygon mark

Description

Draws closed shapes from x/y vertices. Rows that share a value of group are the vertices of one polygon, joined in row order, and the last vertex is joined back to the first. Without a group mapping, all rows form one polygon. Mapping color fills each polygon by its value; a polygon whose rows have different colours is split into one polygon per colour.

Each polygon is one element: its tooltip shows the polygon rather than a single vertex, and brushing or clicking it selects all of its rows. A tooltip template can use any column that has the same value on every row of the polygon, such as a name or an id. Rows with a missing x or y are dropped first, with a warning, and polygons left with fewer than three vertices are not drawn.

Usage

mark_polygon(spec, ..., data = NULL, style = list(), radius = 0)

Arguments

spec	A glyph_spec
...	Aesthetic mappings: x and y (required, numeric), group and color.
data	Optional per-mark data override
style	Named list of fixed visual properties: fill (a colour used when color isn't mapped), stroke (outline colour, the theme's foreground colour by default), stroke_width (in pixels, 0 for no outline) and opacity (of the fill).
radius	Radius of rounded corners, in pixels. Each corner is rounded by at most half the length of its shorter edge. 0 (the default) keeps sharp corners.

Value

Modified glyph_spec object with the polygon mark added

Examples

triangles <- data.frame(
  id = rep(c("a", "b"), each = 3),
  x = c(0, 1, 0.5, 1.5, 2.5, 2),
  y = c(0, 0, 1, 0, 0, 1)
)
glyph(triangles, x = x, y = y) |>
  mark_polygon(group = id, color = id)

glyph documentation built on Oct. 21, 2026, 5:12 p.m.