PostgreSQL Postgis R GeoJSON example

read geo file

# Postgis data type in my case is WSG84: geom | geometry(Point,4326) 
library(jsonlite)
library(RPostgreSQL)
source("dbConnect.R") # create some connection object called con

p <- dbGetQuery(con,
                "SELECT id,
                postal_code,
                st_asGeoJSON(geom)
                FROM sometable
                ORDER BY geom ASC")

p$lng <- sapply(p$st_asgeojson,function(x){
  tryCatch({fromJSON(x)$coordinates[1]},
           error = function(e) NA)
})

p$lat <- sapply(p$st_asgeojson,function(x){
  tryCatch({fromJSON(x)$coordinates[2]},
           error = function(e) NA)
})