Compute the extreme coordinates of geometries

Returns a struct array with four point fields – x_min, x_max, y_min and y_max – giving the coordinate that is furthest in each direction. The result has one row per input geometry; a null or empty geometry yields a row of four nulls.

Usage

ga_extremes(x)

Arguments

x

a GeoArrow geometry array

Value

an Arrow struct array of four point fields, with one row per geometry

Details

Note these are the extreme coordinates, not the corners of the bounding box: the x_min point carries the y value of whichever vertex was leftmost. Use ga_bounding_rect() for the envelope.

References

Extremes

See also

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

Examples

fp <- system.file("shape/nc.shp", package = "sf")
nc <- as.data.frame(read_shapefile(fp))

# one row per county, four point columns
head(as.data.frame(ga_extremes(nc$geometry)), 3)
#>                              x_min                            x_max
#> 1 <POINT (-81.7410736 36.3917847)> <POINT (-81.2398911 36.3653641)>
#> 2 <POINT (-81.3475418 36.5379143)> <POINT (-80.9034424 36.5652122)>
#> 3 <POINT (-80.9657745 36.4672203)> <POINT (-80.4353104 36.5510445)>
#>                              y_min                            y_max
#> 1 <POINT (-81.4727554 36.2343559)> <POINT (-81.6699982 36.5896492)>
#> 2 <POINT (-81.2398911 36.3653641)> <POINT (-81.3452988 36.5728645)>
#> 3  <POINT (-80.874382 36.2338829)> <POINT (-80.9034424 36.5652122)>