Buffer geometries by a given distance

Expands each geometry outward by distance to produce a multipolygon. Line cap and join styles control the shape of the buffer at endpoints and corners.

Usage

ga_buffer(
  geometry,
  distance,
  line_cap = "round",
  line_join = "round",
  miter_limit = 2,
  round_angle = 0.2
)

Arguments

geometry

a GeoArrow geometry array

distance

a numeric vector of buffer distances; length 1 or the same length as geometry

line_cap

one of "round", "square", or "butt"

line_join

one of "round", "miter", or "bevel"

miter_limit

the miter limit used when line_join is "miter"

round_angle

the angular step in radians used to approximate curves when line_cap or line_join is "round". Smaller is smoother

Value

a GeoArrow multipolygon array

References

Buffer

See also

Other misc: ga_centroid(), ga_chaikin_smoothing(), ga_line_segmentize(), ga_remove_repeated_points()

Examples

sq <- geoarrow::as_geoarrow_array(sf::st_sfc(
  sf::st_polygon(list(rbind(c(0, 0), c(2, 0), c(2, 2), c(0, 2), c(0, 0))))
))

# the 2x2 square grows by 8 along its sides plus a unit circle at the corners
as.vector(ga_unsigned_area(ga_buffer(sq, 1)))
#> [1] 15.12145

# a smaller angular step rounds the corners more finely
as.vector(ga_unsigned_area(ga_buffer(sq, 1, round_angle = 0.01)))
#> [1] 15.14108

# square corners instead
as.vector(ga_unsigned_area(ga_buffer(sq, 1, line_join = "bevel")))
#> [1] 14