maps with geojsonio

Scott Chamberlain

2024-11-27

geojsonio creates geojson from various inputs - and can easily feed into tools for making maps with geojson data.

library("geojsonio")

Mapping with leaflet

With geojsonio::map_leaf()

From a file

file <- "myfile.geojson"
geojson_write(us_cities[1:20, ], lat='lat', lon='long', file = file)
map_leaf(as.location(file))

From a SpatialGridDataFrame

sgdim <- c(3, 4)
sg <- SpatialGrid(GridTopology(rep(0, 2), rep(10, 2), sgdim))
sgdf <- SpatialGridDataFrame(sg, data.frame(val = 1:12))
map_leaf(sgdf)

DIY

Example 1: Map of California

library("leaflet")
file <- system.file("examples", "california.geojson", package = "geojsonio")
out <- as.json(geojson_read(file))
leaflet() %>% 
  addProviderTiles("Stamen.Toner") %>% 
  setView(lng = -119, lat = 37, zoom = 6) %>%
  addGeoJSON(out)

Example 2: Map of two polygons

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)
json <- geojson_json(sp_poly)

leaflet() %>% 
  addProviderTiles("Stamen.Toner") %>% 
  setView(lng = -90, lat = 41, zoom = 4) %>%
  addGeoJSON(json)

Mapping with GitHub gists

data.frame

Also, can do so from data.frames with polygons, lists, matrices, vectors, and json strings

map_gist(us_cities)

SpatialPoints class

library("sp")
x <- c(1,2,3,4,5)
y <- c(3,2,5,1,4)
s <- SpatialPoints(cbind(x,y))
map_gist(s)

SpatialPixelsDataFrame class

library("sp")
pixelsdf <- suppressWarnings(
 SpatialPixelsDataFrame(points = canada_cities[c("long", "lat")], data = canada_cities)
)
map_gist(pixelsdf)

Many other spatial classes supported