Read geojson or other formats from a local file or a URL
Arguments
- x
(character) Path to a local file or a URL.
- parse
(logical) To parse geojson to data.frame like structures if possible. Default:
FALSE
- what
(character) What to return. One of "list", "sp" (for Spatial class), or "json". Default: "list". "list" "and" sp run through package sf. if "json", returns json as character class
- stringsAsFactors
Convert strings to Factors? Default
FALSE
.- query
(character) A SQL query, see also postgis
- ...
Further args passed on to
sf::st_read()
Value
various, depending on what's chosen in what
parameter
list: geojson as a list using
jsonlite::fromJSON()
sp: geojson as an sp class object using
sf::st_read()
json: geojson as character string, to parse downstream as you wish
Details
This function supports various geospatial file formats from a URL, as well as local kml, shp, and geojson file formats.
File size
We previously used file_to_geojson()
in this function, leading to
file size problems; this should no longer be a concern, but let us know
if you run into file size problems
Examples
if (FALSE) { # \dontrun{
# From a file
file <- system.file("examples", "california.geojson", package = "geojsonio")
(out <- geojson_read(file))
geojson_read(file)
# From a URL
url <- "https://raw.githubusercontent.com/glynnbird/usstatesgeojson/master/california.geojson"
geojson_read(url)
geojson_read(url, parse = TRUE)
# Use as.location first if you want
geojson_read(as.location(file))
# output a SpatialClass object
## read kml
file <- system.file("examples", "norway_maple.kml", package = "geojsonio")
geojson_read(as.location(file), what = "sp")
## read geojson
file <- system.file("examples", "california.geojson", package = "geojsonio")
geojson_read(as.location(file), what = "sp")
## read geojson from a url
url <- "https://raw.githubusercontent.com/glynnbird/usstatesgeojson/master/california.geojson"
geojson_read(url, what = "sp")
## read from a shape file
file <- system.file("examples", "bison.zip", package = "geojsonio")
dir <- tempdir()
unzip(file, exdir = dir)
shpfile <- list.files(dir, pattern = ".shp", full.names = TRUE)
geojson_read(shpfile, what = "sp")
x <- "https://raw.githubusercontent.com/johan/world.geo.json/master/countries.geo.json"
geojson_read(x, what = "sp")
geojson_read(x, what = "list")
utils::download.file(x, destfile = basename(x))
geojson_read(basename(x), what = "sp")
# from a Postgres database - your Postgres instance must be running
## MAKE SURE to run the setup in the postgis manual file first!
if (requireNamespace("DBI") && requireNamespace("RPostgres")) {
library(DBI)
conn <- tryCatch(dbConnect(RPostgres::Postgres(), dbname = "postgistest"),
error = function(e) e
)
if (inherits(conn, "PqConnection")) {
state <- "SELECT row_to_json(fc)
FROM (SELECT 'FeatureCollection' As type, array_to_json(array_agg(f)) As features
FROM (SELECT 'Feature' As type
, ST_AsGeoJSON(lg.geog)::json As geometry
, row_to_json((SELECT l FROM (SELECT loc_id, loc_name) As l
)) As properties
FROM locations As lg ) As f ) As fc;"
json <- geojson_read(conn, query = state, what = "json")
map_leaf(json)
}
}
} # }