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Convert many input types with spatial data to a geojson file

Source: R/geojson_write.r
geojson_write.Rd

Convert many input types with spatial data to a geojson file

Usage

geojson_write(
  input,
  lat = NULL,
  lon = NULL,
  geometry = "point",
  group = NULL,
  file = "myfile.geojson",
  overwrite = TRUE,
  precision = NULL,
  convert_wgs84 = FALSE,
  crs = NULL,
  ...
)

Arguments

input

Input list, data.frame, spatial class, or sf class. Inputs can also be dplyr tbl_df class since it inherits from data.frame

lat

(character) Latitude name. The default is NULL, and we attempt to guess.

lon

(character) Longitude name. The default is NULL, and we attempt to guess.

geometry

(character) One of point (Default) or polygon.

group

(character) A grouping variable to perform grouping for polygons - doesn't apply for points

file

(character) A path and file name (e.g., myfile), with the .geojson file extension. Default writes to current working directory.

overwrite

(logical) Overwrite the file given in file with input. Default: TRUE. If this param is FALSE and the file already exists, we stop with error message.

precision

desired number of decimal places for the coordinates in the geojson file. Using fewer decimal places can decrease file sizes (at the cost of precision).

convert_wgs84

Should the input be converted to the standard CRS for GeoJSON (https://tools.ietf.org/html/rfc7946) (geographic coordinate reference system, using the WGS84 datum, with longitude and latitude units of decimal degrees; EPSG: 4326). Default is FALSE though this may change in a future package version. This will only work for sf or Spatial objects with a CRS already defined. If one is not defined but you know what it is, you may define it in the crs argument below.

crs

The CRS of the input if it is not already defined. This can be an epsg code as a four or five digit integer or a valid proj4 string. This argument will be ignored if convert_wgs84 is FALSE or the object already has a CRS.

...

Further args passed on to internal functions. For Spatial* classes, data.frames, regular lists, and numerics, it is passed through to sf::st_write(). For sf classes, geo_lists and json classes, it is passed through to jsonlite::toJSON().

Value

A geojson_write class, with two elements:

  • path: path to the file with the GeoJSON

  • type: type of object the GeoJSON came from, e.g., SpatialPoints

See also

geojson_list(), geojson_json(), topojson_write()

Examples

if (FALSE) { # \dontrun{
# From a data.frame
## to points
geojson_write(us_cities[1:2, ], lat = "lat", lon = "long")

## to polygons
head(states)
geojson_write(
  input = states, lat = "lat", lon = "long",
  geometry = "polygon", group = "group"
)

## partial states dataset to points (defaults to points)
geojson_write(input = states, lat = "lat", lon = "long")

## Lists
### list of numeric pairs
poly <- list(
  c(-114.345703125, 39.436192999314095),
  c(-114.345703125, 43.45291889355468),
  c(-106.61132812499999, 43.45291889355468),
  c(-106.61132812499999, 39.436192999314095),
  c(-114.345703125, 39.436192999314095)
)
geojson_write(poly, geometry = "polygon")

### named list
mylist <- list(
  list(latitude = 30, longitude = 120, marker = "red"),
  list(latitude = 30, longitude = 130, marker = "blue")
)
geojson_write(mylist)

# From a numeric vector of length 2
## Expected order is lon, lat
vec <- c(-99.74, 32.45)
geojson_write(vec)

## polygon from a series of numeric pairs
### this requires numeric class input, so inputting a list will
### dispatch on the list method
poly <- c(
  c(-114.345703125, 39.436192999314095),
  c(-114.345703125, 43.45291889355468),
  c(-106.61132812499999, 43.45291889355468),
  c(-106.61132812499999, 39.436192999314095),
  c(-114.345703125, 39.436192999314095)
)
geojson_write(poly, geometry = "polygon")

# Write output of geojson_list to file
res <- geojson_list(us_cities[1:2, ], lat = "lat", lon = "long")
class(res)
geojson_write(res)

# Write output of geojson_json to file
res <- geojson_json(us_cities[1:2, ], lat = "lat", lon = "long")
class(res)
geojson_write(res)

# 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)
geojson_write(sp_poly)

# From SpatialPolygonsDataFrame class
sp_polydf <- as(sp_poly, "SpatialPolygonsDataFrame")
geojson_write(input = sp_polydf)

# From SpatialGrid
x <- GridTopology(c(0, 0), c(1, 1), c(5, 5))
y <- SpatialGrid(x)
geojson_write(y)

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


# From SpatialPixels
library("sp")
pixels <- suppressWarnings(SpatialPixels(SpatialPoints(us_cities[c("long", "lat")])))
summary(pixels)
geojson_write(pixels)

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


# From sf classes:
if (require(sf)) {
  file <- system.file("examples", "feature_collection.geojson", package = "geojsonio")
  sf_fc <- st_read(file, quiet = TRUE)
  geojson_write(sf_fc)
}
} # }