geojsonio (version 0.1.8)

geojson_json: Convert many input types with spatial data to geojson specified as a json string

Description

Convert many input types with spatial data to geojson specified as a json string

Usage

geojson_json(input, lat = NULL, lon = NULL, group = NULL, geometry = "point", type = "FeatureCollection", ...)

Arguments

input

Input list, data.frame, or spatial 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.

group

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

geometry

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

type

(character)The type of collection. One of FeatureCollection (default) or GeometryCollection.

...

Further args passed on to toJSON

Value

An object of class geo_json (and json)

Details

This function creates a geojson structure as a json character string; it does not write a file using rgdal - see geojson_write for that.

Note that all sp class objects will output as FeatureCollection objects, while other classes (numeric, list, data.frame) can be output as FeatureCollection or GeometryCollection objects. We're working on allowing GeometryCollection option for sp class objects.

Also note that with sp classes we do make a round-trip, using writeOGR to write GeoJSON to disk, then read it back in. This is fast and we don't have to think about it too much, but this disk round-trip is not ideal.

Examples

## Not run: 
# # From a numeric vector of length 2, making a point type
# geojson_json(c(-99.74,32.45), pretty=TRUE)
# geojson_json(c(-99.74,32.45), type = "GeometryCollection", pretty=TRUE)
# 
# ## polygon type
# ### 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_json(poly, geometry = "polygon", pretty=TRUE)
# 
# # Lists
# ## From a list of numeric vectors to a polygon
# vecs <- list(c(100.0,0.0), c(101.0,0.0), c(101.0,1.0), c(100.0,1.0), c(100.0,0.0))
# geojson_json(vecs, geometry="polygon", pretty=TRUE)
# 
# ## from a named list
# mylist <- list(list(latitude=30, longitude=120, marker="red"),
#                list(latitude=30, longitude=130, marker="blue"))
# geojson_json(mylist, lat='latitude', lon='longitude')
# 
# # From a data.frame to points
# geojson_json(us_cities[1:2,], lat='lat', lon='long', pretty=TRUE)
# geojson_json(us_cities[1:2,], lat='lat', lon='long',
#    type="GeometryCollection", pretty=TRUE)
# 
# # from data.frame to polygons
# head(states)
# ## make list for input to e.g., rMaps
# geojson_json(states[1:351, ], lat='lat', lon='long', geometry="polygon", group='group')
# 
# # from a geo_list
# a <- geojson_list(us_cities[1:2,], lat='lat', lon='long')
# geojson_json(a)
# 
# # sp classes
# 
# ## 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_json(sp_poly)
# geojson_json(sp_poly, pretty=TRUE)
# 
# ## Another SpatialPolygons
# library("sp")
# library("rgeos")
# pt <- SpatialPoints(coordinates(list(x = 0, y = 0)), CRS("+proj=longlat +datum=WGS84"))
# ## transfrom to web mercator becuase geos needs project coords
# crs <- gsub("\n", "", paste0("+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
#    +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs", collapse = ""))
# pt <- spTransform(pt, CRS(crs))
# ## buffer
# pt <- gBuffer(pt, width = 100)
# pt <- spTransform(pt, CRS("+proj=longlat +datum=WGS84"))
# geojson_json(pt)
# 
# ## data.frame to geojson
# geojson_write(us_cities[1:2,], lat='lat', lon='long') %>% as.json
# 
# # From SpatialPoints class
# x <- c(1,2,3,4,5)
# y <- c(3,2,5,1,4)
# s <- SpatialPoints(cbind(x,y))
# geojson_json(s)
# 
# ## From SpatialPointsDataFrame class
# s <- SpatialPointsDataFrame(cbind(x,y), mtcars[1:5,])
# geojson_json(s)
# 
# ## From SpatialLines class
# library("sp")
# c1 <- cbind(c(1,2,3), c(3,2,2))
# c2 <- cbind(c1[,1]+.05,c1[,2]+.05)
# c3 <- cbind(c(1,2,3),c(1,1.5,1))
# L1 <- Line(c1)
# L2 <- Line(c2)
# L3 <- Line(c3)
# Ls1 <- Lines(list(L1), ID = "a")
# Ls2 <- Lines(list(L2, L3), ID = "b")
# sl1 <- SpatialLines(list(Ls1))
# sl12 <- SpatialLines(list(Ls1, Ls2))
# geojson_json(sl1)
# geojson_json(sl12)
# 
# ## From SpatialLinesDataFrame class
# dat <- data.frame(X = c("Blue", "Green"),
#                  Y = c("Train", "Plane"),
#                  Z = c("Road", "River"), row.names = c("a", "b"))
# sldf <- SpatialLinesDataFrame(sl12, dat)
# geojson_json(sldf)
# geojson_json(sldf, pretty=TRUE)
# 
# ## From SpatialGrid
# x <- GridTopology(c(0,0), c(1,1), c(5,5))
# y <- SpatialGrid(x)
# geojson_json(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_json(sgdf)
# 
# # From SpatialRings
# library("rgeos")
# r1 <- Ring(cbind(x=c(1,1,2,2,1), y=c(1,2,2,1,1)), ID="1")
# r2 <- Ring(cbind(x=c(1,1,2,2,1), y=c(1,2,2,1,1)), ID="2")
# r1r2 <- SpatialRings(list(r1, r2))
# geojson_json(r1r2)
# 
# # From SpatialRingsDataFrame
# dat <- data.frame(id = c(1,2), value = 3:4)
# r1r2df <- SpatialRingsDataFrame(r1r2, data = dat)
# geojson_json(r1r2df)
# 
# # From SpatialPixels
# library("sp") 
# pixels <- suppressWarnings(SpatialPixels(SpatialPoints(us_cities[c("long", "lat")])))
# summary(pixels)
# geojson_json(pixels)
# 
# # From SpatialPixelsDataFrame
# library("sp")
# pixelsdf <- suppressWarnings(
#  SpatialPixelsDataFrame(points = canada_cities[c("long", "lat")], data = canada_cities)
# )
# geojson_json(pixelsdf)
# 
# # From SpatialCollections
# library("sp")
# library("rgeos")
# pts <- SpatialPoints(cbind(c(1,2,3,4,5), c(3,2,5,1,4)))
# 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")
# poly <- SpatialPolygons(list(poly1, poly2), 1:2)
# dat <- SpatialCollections(pts, polygons = poly)
# geojson_json(dat)
# 
# ## Pretty print a json string
# geojson_json(c(-99.74,32.45))
# geojson_json(c(-99.74,32.45)) %>% pretty
# ## End(Not run)