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Build multipolygons from coordinate columns

Source: R/extendr-wrappers.R
ga_multipolygon.Rd

Returns one multipolygon per run of multipolygon_id, with one polygon per run of polygon_id inside it and one ring per run of linestring_id inside each polygon.

Usage

ga_multipolygon(
  x,
  y,
  z = NULL,
  m = NULL,
  multipolygon_id = NULL,
  polygon_id = NULL,
  linestring_id = NULL,
  close = TRUE,
  crs = NULL
)

Arguments

x, y

numeric vectors or float64 arrays of coordinates, one row per vertex

z, m

numeric vectors or float64 arrays of z and m values, or NULL to leave out that dimension

multipolygon_id

a numeric vector, character vector, or Arrow array naming the multipolygon of each row, or NULL for a single multipolygon

polygon_id

a numeric vector, character vector, or Arrow array naming the polygon of each row within its multipolygon, or NULL for one polygon per multipolygon

linestring_id

a numeric vector, character vector, or Arrow array naming the ring of each row within its polygon, or NULL for one ring per polygon

close

whether to close each open ring by repeating its first coordinate

crs

a coordinate reference system to record, or NULL for none

Value

a GeoArrow multipolygon array with one element per multipolygon

Details

ga_multipolygon() matches sfheaders::sf_multipolygon(), taking the columns themselves rather than a data frame and their names. You must keep the rows of each multipolygon together: ga_multipolygon() errors when a multipolygon_id returns after a different one, and orders the multipolygons by where each id first appears. It starts a new polygon at the start of each multipolygon and wherever polygon_id changes, and a new ring at the start of each polygon and wherever linestring_id changes. It takes the first ring of each polygon as its exterior and the rest as holes.

ga_multipolygon() closes rings the way ga_polygon() does, and adds the z and m dimensions when you supply z and m. It errors on NA in any coordinate or id.

See also

Other construct: ga_linestring(), ga_make_envelope(), ga_make_grid(), ga_make_line(), ga_make_line_agg(), ga_make_polygon(), ga_multilinestring(), ga_multipoint(), ga_point(), ga_polygon()

Examples

# two squares in one multipolygon, then a triangle on its own
polys <- ga_multipolygon(
  c(0, 1, 1, 0, 5, 6, 6, 5, 20, 30, 20),
  c(0, 0, 1, 1, 5, 5, 6, 6, 0, 0, 10),
  multipolygon_id = c(1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2),
  polygon_id = c(1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1)
)
sf::st_as_sfc(geoarrow::as_geoarrow_vctr(polys))
#> Geometry set for 2 features 
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: 0 ymin: 0 xmax: 30 ymax: 10
#> CRS:           NA
#> MULTIPOLYGON (((0 0, 1 0, 1 1, 0 1, 0 0)), ((5 ...
#> MULTIPOLYGON (((20 0, 30 0, 20 10, 20 0)))