geojsonio (version 0.1.8)

geojson_list: Convert many input types with spatial data to geojson specified as a list

Description

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

Usage

geojson_list(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.

...

Ignored

Details

This function creates a geojson structure as an R list; 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.

For list and data.frame objects, you don't have to pass in lat and lon parameters if they are named appropriately (e.g., lat/latitude, lon/long/longitude), as they will be auto-detected. If they can not be found, the function will stop and warn you to specify the parameters specifically.

Examples

## Not run: 
# # From a numeric vector of length 2 to a point
# vec <- c(-99.74,32.45)
# geojson_list(vec)
# 
# # Lists
# ## From a list
# mylist <- list(list(latitude=30, longitude=120, marker="red"),
#                list(latitude=30, longitude=130, marker="blue"))
# geojson_list(mylist)
# 
# ## 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_list(vecs, geometry="polygon")
# 
# # from data.frame to points
# (res <- geojson_list(us_cities[1:2,], lat='lat', lon='long'))
# as.json(res)
# ## guess lat/long columns
# geojson_list(us_cities[1:2,])
# geojson_list(states[1:3,])
# geojson_list(states[1:351,], geometry="polygon", group='group')
# geojson_list(canada_cities[1:30,])
# ## a data.frame with columsn not named appropriately, but you can specify them
# # dat <- data.frame(a = c(31, 41), b = c(-120, -110))
# # geojson_list(dat)
# # geojson_list(dat, lat="a", lon="b")
# 
# # from data.frame to polygons
# head(states)
# geojson_list(states[1:351, ], lat='lat', lon='long', geometry="polygon", group='group')
# 
# # 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_list(sp_poly)
# 
# # From SpatialPolygonsDataFrame class
# sp_polydf <- as(sp_poly, "SpatialPolygonsDataFrame")
# geojson_list(input = sp_polydf)
# 
# # From SpatialPoints class
# x <- c(1,2,3,4,5)
# y <- c(3,2,5,1,4)
# s <- SpatialPoints(cbind(x,y))
# geojson_list(s)
# 
# # From SpatialPointsDataFrame class
# s <- SpatialPointsDataFrame(cbind(x,y), mtcars[1:5,])
# geojson_list(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_list(sl1)
# geojson_list(sl12)
# as.json(geojson_list(sl12))
# as.json(geojson_list(sl12), pretty=TRUE)
# 
# # 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_list(sldf)
# as.json(geojson_list(sldf))
# as.json(geojson_list(sldf), pretty=TRUE)
# 
# # From SpatialGrid
# x <- GridTopology(c(0,0), c(1,1), c(5,5))
# y <- SpatialGrid(x)
# geojson_list(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_list(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_list(r1r2)
# 
# # From SpatialRingsDataFrame
# dat <- data.frame(id = c(1,2), value = 3:4)
# r1r2df <- SpatialRingsDataFrame(r1r2, data = dat)
# geojson_list(r1r2df)
# 
# # From SpatialPixels
# library("sp")
# pixels <- suppressWarnings(SpatialPixels(SpatialPoints(us_cities[c("long", "lat")])))
# summary(pixels)
# geojson_list(pixels)
# 
# # From SpatialPixelsDataFrame
# library("sp")
# pixelsdf <- suppressWarnings(
#  SpatialPixelsDataFrame(points = canada_cities[c("long", "lat")], data = canada_cities)
# )
# geojson_list(pixelsdf)
# 
# # From SpatialCollections
# 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")
# poly <- SpatialPolygons(list(poly1, poly2), 1:2)
# coordinates(us_cities) <- ~long+lat
# dat <- SpatialCollections(points = us_cities, polygons = poly)
# out <- geojson_list(dat)
# out$SpatialPoints
# out$SpatialPolygons
# ## End(Not run)