geojson operations

In geojson: Classes for 'GeoJSON'

knitr::opts_chunk$set(
  comment = "#>",
  collapse = TRUE,
  warning = FALSE,
  message = FALSE
)

The geojson package has functions to do basic operations on GeoJSON classes.

library("geojson")

First, let's make a GeoJSON object

x <- '{
 "type": "GeometryCollection",
 "geometries": [
   {
     "type": "Point",
     "coordinates": [100.0, 0.0]
   },
   {
     "type": "LineString",
     "coordinates": [ [101.0, 0.0], [102.0, 1.0] ]
   }
  ]
}'
(y <- geometrycollection(x))

inspect the object

Get the string

y[[1]]

Get the type

geo_type(y)

Pretty print the geojson

geo_pretty(y)

Write to disk

geo_write(y, f <- tempfile(fileext = ".geojson"))
jsonlite::fromJSON(f, FALSE)

unlink(f)

properties

Add properties

x <- '{ "type": "LineString", "coordinates": [ [100.0, 0.0], [101.0, 1.0] ]}'
res <- linestring(x) %>% feature() %>% properties_add(population = 1000)
res

Get a property

properties_get(res, property = 'population')

crs

Add crs

crs <- '{
  "type": "name",
  "properties": {
     "name": "urn:ogc:def:crs:OGC:1.3:CRS84"
  }
}'
z <- x %>% feature() %>% crs_add(crs)
z

Get crs

crs_get(z)

bbox

Add bbox - by default, if you don't pass a bbox into bbox_add() we attempt to calculate the bbox for you. You can also pass in your own bbox.

tt <- x %>% feature() %>% bbox_add()
tt

Get bbox

bbox_get(tt)

geojson in data.frame's

It's really easy to put geojson class objects into data.frame's as well.

The ideal solution is to put them into tbl's (see the tibble package)

Make a point

x <- '{ "type": "Point", "coordinates": [100.0, 0.0] }'
(pt <- point(x))

Put the point into a tbl

library("tibble")
data_frame(a = 1:5, b = list(pt))

Another object, here a multilinestring

x <- '{ "type": "MultiLineString",
  "coordinates": [ [ [100.0, 0.0], [101.0, 1.0] ], [ [102.0, 2.0], [103.0, 3.0] ] ] }'
(mls <- multilinestring(x))

Put into a tbl

data_frame(a = 1:5, b = list(mls))

Put the point and multilinestring into the same tbl

(df <- data_frame(a = 1:5, b = list(pt), c = list(mls)))

And you can pull the geojson back out

df$b
df$b[[1]]

geojson documentation built on Aug. 8, 2023, 5:11 p.m.