Extracts the exterior ring of polygon geometries — ddbs_exterior

Returns the exterior ring (outer boundary) of polygon geometries from a DuckDB table using the spatial extension. For multi-polygons, returns the exterior ring of each polygon component. Returns the result as an sf object or creates a new table in the database.

Usage

ddbs_exterior_ring(
  x,
  conn = NULL,
  name = NULL,
  crs = NULL,
  crs_column = "crs_duckspatial",
  overwrite = FALSE,
  quiet = FALSE
)

Arguments

x: An sf spatial object. Alternatively, it can be a string with the name of a table with geometry column within the DuckDB database conn. Data is returned from this object.
conn: A connection object to a DuckDB database. If NULL, the function runs on a temporary DuckDB database.
name: A character string of length one specifying the name of the table, or a character string of length two specifying the schema and table names. If NULL (the default), the function returns the result as an sf object
crs: The coordinates reference system of the data. Specify if the data doesn't have a crs_column, and you know the CRS.
crs_column: a character string of length one specifying the column storing the CRS (created automatically by ddbs_write_vector). Set to NULL if absent.
overwrite: Boolean. whether to overwrite the existing table if it exists. Defaults to FALSE. This argument is ignored when name is NULL.
quiet: A logical value. If TRUE, suppresses any informational messages. Defaults to FALSE.

Value

an sf object or TRUE (invisibly) for table creation

Examples

if (FALSE) { # \dontrun{
## load packages
library(duckspatial)
library(sf)

# create a duckdb database in memory (with spatial extension)
conn <- ddbs_create_conn(dbdir = "memory")

## read data
countries_sf <- st_read(system.file("spatial/countries.geojson", package = "duckspatial"))

## store in duckdb
ddbs_write_vector(conn, countries_sf, "countries")

## extract exterior ring
ddbs_exterior_ring(conn = conn, "countries")

## extract exterior ring without using a connection
ddbs_exterior_ring(countries_sf)
} # }