Geometry without the data

Sometimes you just want the canvas: country polygons, label-ready centroids, coastlines, internal borders, a graticule or an ocean rectangle – already projected, region-subset and antimeridian-safe. This is the building block the plotting functions sit on, exposed for power users.

Usage

world_geometry(
  what = c("countries", "centroids", "coastline", "borders", "graticule", "ocean"),
  geometry = c("polygon", "sf"),
  scale = "small",
  region = NULL,
  projection = "equal_earth",
  recenter = NULL
)

Arguments

what

What to return: "countries" (default), "centroids", "coastline", "borders", "graticule" or "ocean".

geometry

"polygon" (a tibble of long/lat/group) or "sf".

scale

Natural Earth resolution for the sf backend: "small" (110m), "medium" (50m) or "large" (10m). "large" additionally needs the rnaturalearthhires package, which is not on CRAN (install.packages("rnaturalearthhires", repos = "https://ropensci.r-universe.dev")); "small" and "medium" need nothing beyond rnaturalearthdata. Coarser scales carry fewer countries as well as less detail – see attach_geometry().

region

Optional subset: a continent, a group name, a vector of iso3c codes, or a bounding box c(xmin, ymin, xmax, ymax). A box is the one form that clips the shapes themselves rather than selecting whole countries – properly, via sf::st_crop(), on the sf backend. The polygon backend can only drop the vertices outside the box, which leaves a country straddling the edge with an approximate outline, so it warns.

projection

Projection for the sf backend (see world_map()).

recenter

Optional central meridian for a recentred map (e.g. 150).

Value

A tibble (polygon backend) or sf object (sf backend), with columns depending on what:

"countries"

polygon: long, lat, group, order, region, subregion, iso3c, iso2c. sf: iso3c, iso2c, name_long.

"centroids"

the same identifier columns plus centroid_lon and centroid_lat.

"coastline", "borders", "ocean", "graticule"

sf only.

The centroid columns are in the coordinate system of the object returned, so on the sf backend they are projected metres, not degrees – centroid_lon for France is 174097, not 2.1. For centroids in degrees use country_meta$centroid_lon / $centroid_lat, which is also what the polygon backend returns.

A few Natural Earth features have no ISO code and so come back with iso3c NA – Somaliland at every scale, plus the Indian Ocean Territories and Ashmore and Cartier Islands from "medium" on. They are kept so the land is still drawn; drop or country_overrides() them if you group by iso3c.

"orthographic" is the one genuinely hemispheric projection: the countries on the far side have no image and come back as empty geometries (correctly, but sf::st_coordinates() cannot read a column that mixes empty and non-empty – drop them first). The other three azimuthal projections ("azimuthal_equal_area", "north_polar", "south_polar") are Lambert equal-area and draw the whole globe, the far side stretched around the rim rather than dropped, so pass region if you want a polar view of the northern countries alone.

"ocean" is a whole-globe background rectangle. It is unavailable in all four azimuthal projections – "orthographic" has no image for it, and the Lambert three cut the globe at the antipode, which collapses the rectangle's outline – and it cannot be recentred; both cases error rather than returning an invisible layer.

Examples

# \donttest{
if (requireNamespace("maps", quietly = TRUE)) {
  head(world_geometry("countries", geometry = "polygon"))
}
#> # A tibble: 6 × 8
#>    long   lat group order region subregion iso3c iso2c
#>   <dbl> <dbl> <dbl> <int> <chr>  <chr>     <chr> <chr>
#> 1 -69.9  12.5     1     1 Aruba  NA        ABW   AW   
#> 2 -69.9  12.4     1     2 Aruba  NA        ABW   AW   
#> 3 -69.9  12.4     1     3 Aruba  NA        ABW   AW   
#> 4 -70.0  12.5     1     4 Aruba  NA        ABW   AW   
#> 5 -70.1  12.5     1     5 Aruba  NA        ABW   AW   
#> 6 -70.1  12.6     1     6 Aruba  NA        ABW   AW   
# }