The function sends a query plus an sf layer to PostGIS, saving the trouble of manually importing the layer and exporting the result
st_postgis(x, con, query, prefix = "temporary_nngeo_layer_")Object of class sf
Connection to PostgreSQL database with PostGIS extension enabled. Can be created using function RPostgreSQL::dbConnect
SQL query, which may refer to layer x as x and to the geometry column of the x layer as geom (see examples)
Prefix for storage of temporarily layer in the database
Returned result from the database: an sf layer in case the result includes a geometry column, otherwise a data.frame
if (FALSE) {
# Database connection and 'sf' layer
source("~/Dropbox/postgis_159.R") ## Creates connection object 'con'
x = towns
# Query 1: Buffer
query = "SELECT ST_Buffer(geom, 0.1, 'quad_segs=2') AS geom FROM x LIMIT 5;"
st_postgis(x, con, query)
# Query 2: Extrusion
query = "SELECT ST_Extrude(geom, 0, 0, 30) AS geom FROM x LIMIT 5;"
st_postgis(x, con, query)
}