Load vectorial data from DuckDB into R — ddbs_read

Retrieves the data from a DuckDB table with a geometry column, and convert it to an R sf object.

Usage

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

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.
crs: the coordinates reference system of the data. Specify if the data doesn't have 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.

Value

an sf object

Examples

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

## connect to in memory database
conn <- dbConnect(duckdb::duckdb())

## install the spatial exntesion
ddbs_install(conn)
ddbs_load(conn)

## 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)

## insert data into the database
ddbs_write_vector(conn, sf_points, "points")

## read data back into R
ddbs_read_vector(conn, "points", crs = 4326)

## disconnect from db
dbDisconnect(conn)
}