Returns the concave hull enclosing the geometry — ddbs_concave

Returns the concave hull enclosing the geometry from an sf object or from a DuckDB table using the spatial extension. Returns the result as an sf object or creates a new table in the database.

Usage

ddbs_concave_hull(
  x,
  ratio = 0.5,
  allow_holes = TRUE,
  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.
ratio: Numeric. The ratio parameter dictates the level of concavity; 1 returns the convex hull, while 0 indicates to return the most concave hull possible. Defaults to 0.5.
allow_holes: Boolean. If TRUE (the default), it allows the output to contain holes.
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(duckdb)
library(duckspatial)
library(sf)

# create points data
n <- 5
points_sf <- data.frame(
    id = 1,
    x = runif(n, min = -180, max = 180),
    y = runif(n, min = -90, max = 90)
    ) |>
    sf::st_as_sf(coords = c("x", "y"), crs = 4326) |>
    st_geometry() |>
    st_combine() |>
    st_cast("MULTIPOINT") |>
    st_as_sf()

# option 1: passing sf objects
output1 <- duckspatial::ddbs_concave_hull(x = points_sf)

plot(output1)


# option 2: passing the name of a table in a duckdb db

# creates a duckdb
conn <- duckspatial::ddbs_create_conn()

# write sf to duckdb
ddbs_write_vector(conn, points_sf, "points_tbl")

# spatial join
output2 <- duckspatial::ddbs_concave_hull(
    conn = conn,
    x = "points_tbl"
    )

plot(output2)

} # }