Fast polygon union by ID

Significantly faster than `sf::st_union()`/`dplyr::summarise()` for unioning large polygon datasets by a grouping column, by leveraging `terra`'s `aggregate()` with a round-trip through `terra::vect()`.

Usage

union_polygons(poly, ID)

Arguments

poly

An `sf` POLYGON/MULTIPOLYGON object with an attribute column used for grouping.

ID

A string naming the column over which to union geometries.

Value

An `sf` polygon layer unioned by `ID` (column preserved).

Notes

If any resulting geometries are geometry collections, they are extracted to POLYGON using `sf::st_collection_extract()`.

Examples

if (FALSE) { # \dontrun{
out <- union_polygons(counties_sf, "state_fips")
} # }