Compute the bounding box of geometries

Returns the axis aligned bounding box of each geometry, as the box array that the spatial index queries take.

Usage

ga_envelope(x)

Arguments

x

a GeoArrow geometry array

Value

a GeoArrow box array of the same length as x

Details

A box array is passed straight through rather than recomputed, so this is cheap to call on something that already holds boxes and safe to call defensively before a query.

This is the envelope in the OGC sense. It differs from ga_bounding_rect() only in that pass through; the boxes themselves are the same.

See also

Other index: KDTree, RTree, ga_knn_join(), ga_set_thread_pool(), ga_sparse_dwithin(), ga_sparse_knn()

Examples

nc <- as.data.frame(read_shapefile(
  system.file("shape/nc.shp", package = "sf")
))
boxes <- ga_envelope(nc$geometry)
head(geoarrow::as_geoarrow_vctr(boxes), 3)
#> <geoarrow_vctr geoarrow.box{struct}[3]>
#> [1] <POLYGON ((-81.7410736 36.2343559, -81.2398911 36.2343559, -81.2398911 >
#> [2] <POLYGON ((-81.3475418 36.3653641, -80.9034424 36.3653641, -80.9034424 >
#> [3] <POLYGON ((-80.9657745 36.2338829, -80.4353104 36.2338829, -80.4353104 >

# already boxes, so this is a no op
identical(
  as.character(geoarrow::as_geoarrow_vctr(ga_envelope(boxes))),
  as.character(geoarrow::as_geoarrow_vctr(boxes))
)
#> [1] TRUE