Read and write from R to postgresql/postgis

readwrite_sf.R

library(sf)
library(RPostgreSQL)
dat <- data.frame(ID = 1:2,
                  long = c(-74.003234, -73.983317), 
                  lat = c(40.731863, 40.722684))
dat_sf <- st_as_sf(dat, coords = c("long", "lat"), 
                   crs = 4326, 
                   agr = "identity")
con <- dbConnect(PostgreSQL(), dbname = "mydb", host = "localhost")
st_write_db(con, dat_sf, "mydata")
dbListTables(con) # [1] "spatial_ref_sys" "mydata"   
new_dat <- st_read_db(con, "mydata")