At rOpenSci we’ve been working on an R package (geojsonio) to make converting R data in various formats to geoJSON and topoJSON, and vice versa. We hope to do this one job very well, and handle all reasonable use cases.

Functions in this package are organized first around what you’re working with or want to get, geojson or topojson, then convert to or read from various formats:

  • geojson_list()/topojson_list() - convert to geojson/topojson as R list format
  • geojson_json()/topojson_json() - convert to geojson/topojson as json
  • geojson_read()``topojson_read() - read a geojson/topojson file from file path or URL
  • geojson_write()/topojson_write() - write a geojson/topojson file locally

Each of the above functions have methods for various objects/classes, including numeric, data.frame, list, SpatialPolygons, SpatialPolygonsDataFrame, SpatialLines, SpatialLinesDataFrame, SpatialPoints, SpatialPointsDataFrame.

Install

Install rgdal - in case you can’t get it installed from binary , here’s what works on a Mac.

install.packages("https://cran.r-project.org/src/contrib/rgdal_0.9-1.tar.gz", repos = NULL, type="source", configure.args = "--with-gdal-config=/Library/Frameworks/GDAL.framework/Versions/1.10/unix/bin/gdal-config --with-proj-include=/Library/Frameworks/PROJ.framework/unix/include --with-proj-lib=/Library/Frameworks/PROJ.framework/unix/lib")

Install geojsonio

install.packages("devtools")
devtools::install_github("ropensci/geojsonio")

library("geojsonio")

GeoJSON

Convert various formats to geojson

From a numeric vector of length 2, as json or list

geojson_json(c(32.45,-99.74))
#> {"type":"Point","geometry":{"type":"Point","coordinates":[32.45,-99.74]},"properties":{}}
geojson_list(c(32.45,-99.74))
#> $type
#> [1] "Point"
#> 
#> $geometry
#> $geometry$type
#> [1] "Point"
#> 
#> $geometry$coordinates
#> [1]  32.45 -99.74
#> 
#> 
#> $properties
#> NULL
#> 
#> attr(,"class")
#> [1] "geo_list"
#> attr(,"from")
#> [1] "numeric"

From a data.frame

library('maps')
data(us.cities)
geojson_json(us.cities[1:2,], lat='lat', lon='long')
#> {"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"Point","coordinates":[-99.74,32.45]},"properties":{"name":"Abilene TX","country.etc":"TX","pop":"113888","capital":"0"}},{"type":"Feature","geometry":{"type":"Point","coordinates":[-81.52,41.08]},"properties":{"name":"Akron OH","country.etc":"OH","pop":"206634","capital":"0"}}]}
geojson_list(us.cities[1:2,], lat='lat', lon='long')
#> $type
#> [1] "FeatureCollection"
#> 
#> $features
#> $features[[1]]
#> $features[[1]]$type
#> [1] "Feature"
#> 
#> $features[[1]]$geometry
#> $features[[1]]$geometry$type
#> [1] "Point"
#> 
#> $features[[1]]$geometry$coordinates
#> [1] -99.74  32.45
#> 
#> 
#> $features[[1]]$properties
#> $features[[1]]$properties$name
#> [1] "Abilene TX"
#> 
#> $features[[1]]$properties$country.etc
#> [1] "TX"
#> 
#> $features[[1]]$properties$pop
#> [1] "113888"
#> 
#> $features[[1]]$properties$capital
#> [1] "0"
#> 
#> 
#> 
#> $features[[2]]
#> $features[[2]]$type
#> [1] "Feature"
#> 
#> $features[[2]]$geometry
#> $features[[2]]$geometry$type
#> [1] "Point"
#> 
#> $features[[2]]$geometry$coordinates
#> [1] -81.52  41.08
#> 
#> 
#> $features[[2]]$properties
#> $features[[2]]$properties$name
#> [1] "Akron OH"
#> 
#> $features[[2]]$properties$country.etc
#> [1] "OH"
#> 
#> $features[[2]]$properties$pop
#> [1] "206634"
#> 
#> $features[[2]]$properties$capital
#> [1] "0"
#> 
#> 
#> 
#> 
#> attr(,"class")
#> [1] "geo_list"
#> attr(,"from")
#> [1] "data.frame"

From SpatialPolygons class

library('sp')
poly1 <- Polygons(list(Polygon(cbind(c(-100,-90,-85,-100),
                                     c(40,50,45,40)))), "1")
poly2 <- Polygons(list(Polygon(cbind(c(-90,-80,-75,-90),
                                     c(30,40,35,30)))), "2")
sp_poly <- SpatialPolygons(list(poly1, poly2), 1:2)

to json

geojson_json(sp_poly)
#> {"type":"Polygon","bbox":[-100,-75,30,50],"coordinates":[[[-100,40],[-90,50],[-85,45],[-100,40]],[[-90,30],[-80,40],[-75,35],[-90,30]]],"properties":{}}

to list

geojson_list(sp_poly)$coordinates[[1]]
#> [[1]]
#> [[1]][[1]]
#> [1] -100
#> 
#> [[1]][[2]]
#> [1] 40
#> 
#> 
#> [[2]]
#> [[2]][[1]]
#> [1] -90
#> 
#> [[2]][[2]]
#> [1] 50
#> 
#> 
#> [[3]]
#> [[3]][[1]]
#> [1] -85
#> 
#> [[3]][[2]]
#> [1] 45
#> 
#> 
#> [[4]]
#> [[4]][[1]]
#> [1] -100
#> 
#> [[4]][[2]]
#> [1] 40

Write geojson

library('maps')
data(us.cities)
geojson_write(us.cities[1:2,], lat='lat', lon='long')
#> <geojson>
#>   Path:       myfile.geojson
#>   From class: data.frame

Read geojson

file <- system.file("examples", "california.geojson", package = "geojsonio")
out <- geojson_read(file)
#> OGR data source with driver: GeoJSON 
#> Source: "/Users/sacmac/Library/R/3.1/library/geojsonio/examples/california.geojson", layer: "OGRGeoJSON"
#> with 1 features and 11 fields
#> Feature type: wkbMultiPolygon with 2 dimensions
plot(out)

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TopoJSON

Convert to TopoJSON with Node topojson client

For topojson you will need Mike Bostock’s command line client. Install it by doing

sudo npm install -g topojson

Download a zipped shape fileset, this one for distribution of Quercus wislizeni. Unzip the zip file to a folder. Then do (changing the path to your path)

topojson_write(shppath='~/Downloads/querwisl', path = "~/Downloads", projection='albers', projargs=list(rotate='[60, -35, 0]'))
#> OGR data source with driver: ESRI Shapefile 
#> Source: "/Users/sacmac/Downloads/querwisl", layer: "querwisl"
#> with 35 features and 5 fields
#> Feature type: wkbPolygon with 2 dimensions

Which prints progress on the conversion of the shape file. And prints the topojson CLI call, including the location of the output file, here /Users/sacmac/querwisl.json

OGR data source with driver: ESRI Shapefile
Source: "/Users/sacmac/Downloads/querwisl", layer: "querwisl"
with 35 features and 5 fields
Feature type: wkbPolygon with 2 dimensions
topojson -o /Users/sacmac/querwisl.json -q 1e4 -s 0 --shapefile-encoding utf8 --projection 'd3.geo.albers().rotate([60, -35, 0])' -- /var/folders/gs/4khph0xs0436gmd2gdnwsg080000gn/T//Rtmp49APW7/querwisl.shp

bounds: -403.2554825867553 401.27189387582916 -295.798050380061 585.4214768677039 (cartesian)
pre-quantization: 0.010746817902459677 0.018416799979185387
topology: 35 arcs, 2492 points
prune: retained 35 / 35 arcs (100%)

You can then use this topojson file wherever. We’ll add a function soon to automagically throw this file up as a Github gist to get an interactive map.

Read topojson

TopoJSON

url <- "https://raw.githubusercontent.com/shawnbot/d3-cartogram/master/data/us-states.topojson"
out <- topojson_read(url)
#> OGR data source with driver: GeoJSON 
#> Source: "https://raw.githubusercontent.com/shawnbot/d3-cartogram/master/data/us-states.topojson", layer: "states"
#> with 51 features and 2 fields
#> Feature type: wkbPolygon with 2 dimensions
plot(out)

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Use case: Play with US states

Using data from https://github.com/glynnbird/usstatesgeojson

Get some geojson

library('httr')
res <- GET('https://api.github.com/repos/glynnbird/usstatesgeojson/contents')
st_names <- Filter(function(x) grepl("\\.geojson", x), sapply(content(res), "[[", "name"))
base <- 'https://raw.githubusercontent.com/glynnbird/usstatesgeojson/master/'
st_files <- paste0(base, st_names)

Make a faceted plot

library('ggplot2')
library('plyr')
st_use <- st_files[7:13]
geo <- lapply(st_use, geojson_read, verbose = FALSE)
df <- ldply(setNames(lapply(geo, fortify), gsub("\\.geojson", "", st_names[7:13])))
ggplot(df, aes(long, lat, group = group)) +
  geom_polygon() +
  facet_wrap(~ .id, scales = "free")

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Maps

We’re also working on map_gist() - to push up a geojson or topojson file as a GitHub gist (renders as an interactive map). It still needs some work…

Validate geojson

geojsonlint.com has a nice web interface you can use to make sure you’re geoJSON is in the right format. In addition, it provides a RESTful endpoint at geojsonlint.com/validate to validate geoJSON. This was just added today in this package, and can be used from many data types.

Good geoJSON

validate('{"type": "Point", "coordinates": [-100, 80]}')
#> $status
#> [1] "ok"

Bad geoJSON

validate('{"type": "Rhombus", "coordinates": [[1, 2], [3, 4], [5, 6]]}')
#> $message
#> [1] "\"Rhombus\" is not a valid GeoJSON type."
#> 
#> $status
#> [1] "error"

A file

file <- system.file("examples", "zillow_or.geojson", package = "togeojson")
validate(x = as.location(file))
#> $status
#> [1] "ok"

A URL

url <- "https://raw.githubusercontent.com/glynnbird/usstatesgeojson/master/california.geojson"
validate(as.location(url))
#> $status
#> [1] "ok"

From the output of geojson_list()

library("maps")
data(us.cities)
x <- geojson_list(us.cities[1:2,], lat='lat', lon='long')
validate(x)
#> $status
#> [1] "ok"

From SpatialPoints class

library("sp")
a <- c(1,2,3,4,5)
b <- c(3,2,5,1,4)
x <- SpatialPoints(cbind(a,b))
validate(x)
#> $status
#> [1] "ok"