geojson_read: Read geojson or other formats from a local file or a URL

In geojsonio: Convert Data from and to 'GeoJSON' or 'TopoJSON'

Read geojson or other formats from a local file or a URL

Description

Read geojson or other formats from a local file or a URL

Usage

geojson_read(
  x,
  parse = FALSE,
  what = "list",
  stringsAsFactors = FALSE,
  query = NULL,
  ...
)

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()

Details

This function supports various geospatial file formats from a URL, as well as local kml, shp, and geojson file formats.

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

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

See Also

topojson_read(), geojson_write() postgis

Examples

## Not run: 
# 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)
  }
}

## End(Not run)

geojsonio documentation built on Sept. 8, 2023, 5:54 p.m.