Compute the bounding box of geometries

Returns the axis aligned bounding box of each geometry as a box array, the type 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

ga_envelope() returns a box array as it is instead of recomputing it, so you can call it before a query whether or not the input already holds boxes. It returns NA for a null or empty geometry.

PostGIS calls this ST_Envelope(), which returns a polygon rather than a box.

See also

Other boundary: ga_concave_hull(), ga_convex_hull(), ga_extremes(), ga_minimum_rotated_rect()

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

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 ga_envelope() returns them untouched
identical(
  as.character(geoarrow::as_geoarrow_vctr(ga_envelope(boxes))),
  as.character(geoarrow::as_geoarrow_vctr(boxes))
)
#> [1] TRUE