duckspatial (version 0.9.0)

ddbs_concave_hull: Returns the concave hull enclosing the geometry

Description

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
)

Value

an sf object or TRUE (invisibly) for table creation

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.

Examples

if (FALSE) {
## load packages
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)

}