to_sf {duckdbfs}

Convert output to sf object

Description

Convert output to sf object

Usage

to_sf(x, crs = NA, conn = cached_connection())

Arguments

x

a remote duckdb tbl (from open_dataset) or dplyr-pipeline thereof.

crs

The coordinate reference system, any format understood by sf::st_crs.

conn

the connection object from the tbl. Takes a duckdb table (from open_dataset) or a dataset or dplyr pipline and returns an sf object. Important: the table must have a geometry column, which you will almost always have to create first.

Note: to_sf() triggers collection into R. This function is suitable to use at the end of a dplyr pipeline that will subset the data. Using this function on a large dataset without filtering first may exceed available memory.

Value

an sf class object (in memory).

Examples

library(dplyr)
csv_file <- system.file("extdata/spatial-test.csv", package="duckdbfs")

# Note that we almost always must first create a `geometry` column, e.g.
# from lat/long columns using the `st_point` method.
sf <-
  open_dataset(csv_file, format = "csv") |>
  mutate(geom = ST_Point(longitude, latitude)) |>
  to_sf()

# We can use the full space of spatial operations, including spatial
# and normal dplyr filters.  All operations are translated into a
# spatial SQL query by `to_sf`:
open_dataset(csv_file, format = "csv") |>
  mutate(geom = ST_Point(longitude, latitude)) |>
  mutate(dist = ST_Distance(geom, ST_Point(0,0))) |>
  filter(site %in% c("a", "b", "e")) |>
  to_sf()