Union geometries

Union geometries to create MULTI* geometries in the case of different geometries. If geometries are identical, the union returns a single geometry. If you need to preserve all geometries, use sf::st_combine(). This function behaves differently than sf because it strictly returns 1 or length(x) geometries.

st_union(x, y, by_feature = TRUE)

Arguments

x	A geometry or a set of geometries of class sfc to be unioned.
y	(optional). A geometry or a set of geometries of class sfc.
by_feature	default is TRUE. Union each element of x with corresponding y element. If FALSE, all the features are first unioned row-wise, then all unioned together.

See also

sf::st_union(), sf::st_combine()

Examples

library(tibble)
library(dplyr)

geom <- tibble(
  x = 1:3,
  y = 4:6,
  origin = st_point(x, y),
  destin = st_point(x + 1, y + 1)
)
geom <- mutate(geom, union = st_union(origin, destin))
geom
#> # A tibble: 3 x 5
#>       x     y  origin  destin          union
#>   <int> <int> <POINT> <POINT>   <MULTIPOINT>
#> 1     1     4   (1 4)   (2 5) ((1 4), (2 5))
#> 2     2     5   (2 5)   (3 6) ((2 5), (3 6))
#> 3     3     6   (3 6)   (4 7) ((3 6), (4 7))
summarise(geom, union = st_union(origin, destin, by_feature = FALSE))
#> # A tibble: 1 x 1
#>                          union
#>                   <MULTIPOINT>
#> 1 ((1 4), (2 5), (3 6), (4 7))