duckspatial (version 0.9.0)

ddbs_read_vector: Load spatial vector data from DuckDB into R

Description

Retrieves the data from a DuckDB table, view, or Arrow view with a geometry column, and converts it to an R sf object. This function works with both persistent tables created by ddbs_write_vector and temporary Arrow views created by ddbs_register_vector.

Usage

ddbs_read_vector(
  conn,
  name,
  crs = NULL,
  crs_column = "crs_duckspatial",
  clauses = NULL,
  quiet = FALSE
)

Value

an sf object

Arguments

conn

A connection object to a 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.

clauses

character, additional SQL code to modify the query from the table (e.g. "WHERE ...", "ORDER BY...")

quiet

A logical value. If TRUE, suppresses any informational messages. Defaults to FALSE.

Examples

if (FALSE) { # interactive()
## load packages
library(duckspatial)
library(sf)

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

## create random points
random_points <- data.frame(
  id = 1:5,
  x = runif(5, min = -180, max = 180),
  y = runif(5, min = -90, max = 90)
)

## convert to sf
sf_points <- st_as_sf(random_points, coords = c("x", "y"), crs = 4326)

## Example 1: Write and read persistent table
ddbs_write_vector(conn, sf_points, "points")
ddbs_read_vector(conn, "points", crs = 4326)

## Example 2: Register and read Arrow view (faster, temporary)
ddbs_register_vector(conn, sf_points, "points_view")
ddbs_read_vector(conn, "points_view", crs = 4326)

## disconnect from db
ddbs_stop_conn(conn)
}