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Build star polygons

Source: R/gspace-misc.R
sfshape_stars.Rd

Construct one or more star-shaped polygons, alternating between an outer and an inner radius at each vertex, as sfg/sfc POLYGON geometry. sfshape_star() builds a single star at a given center; sfshape_stars() builds n stars, automatically arranged in a compact, non-overlapping grid. Useful for building varied, non-hand-typed node geometries; see the geometry vignette for examples, and sfshape_ngons for the regular-polygon equivalent.

Usage

sfshape_star(cx = 0, cy = 0, points = 5, r_outer = 0.3, r_inner = 0.1)

sfshape_stars(
  n,
  points = c(3, 4, 5),
  r_outer = 0.3,
  r_inner = 0.1,
  spacing = NULL
)

Arguments

cx, cy

Numeric. Coordinates of the star's center. (sfshape_star() only.)

points

Integer. Number of star points; must be 2 or more. For sfshape_stars(), may be a vector, recycled across the n stars to vary shape per star.

r_outer

Numeric. Radius to each outer (point) vertex. For sfshape_stars(), may be a vector, recycled across the n stars.

r_inner

Numeric. Radius to each inner (valley) vertex. Smaller values relative to r_outer produce sharper points; values closer to r_outer produce a rounder, less pronounced star. For sfshape_stars(), may be a vector, recycled across the n stars.

n

Integer. Number of stars to build. (sfshape_stars() only.)

spacing

Numeric. Distance between star centers in the auto-generated grid. Defaults to max(r_outer) * 2.5, which guarantees no overlap. (sfshape_stars() only.)

Value

sfshape_star() returns a single sfg object of type POLYGON. sfshape_stars() returns an sfc of n such stars.

See also

sfshape_ngons

Examples

star5 <- sfshape_star(0, 0, points = 5, r_outer = 1, r_inner = 0.4)
star8 <- sfshape_star(3, 0, points = 8, r_outer = 1, r_inner = 0.7)
plot(sf::st_sfc(star5, star8))


many <- sfshape_stars(6, points = 5, r_outer = 0.4, r_inner = 0.16)
plot(many)