# Convert many input types with spatial data to geojson specified as a list ```r geojson_list( input, lat = NULL, lon = NULL, group = NULL, geometry = "point", type = "FeatureCollection", convert_wgs84 = FALSE, crs = NULL, precision = 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. - `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. - `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. - `precision`: (integer) desired number of decimal places for coordinates. Only used with classes from `sp` classes; ignored for other classes. Using fewer decimal places decreases object sizes (at the cost of precision). This changes the underlying precision stored in the data. `options(digits = )` changes the maximum number of digits displayed (to find out what yours is set at see `getOption("digits")`); the value of this parameter will change what's displayed in your console up to the value of `getOption("digits")` - `...`: Ignored ## Details This function creates a geojson structure as an R list; it does not write a file - 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 `sf::st_write()` 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 sf classes (sf, sfc, sfg), the following conversions are made: * sfg: the appropriate geometry `Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon,GeometryCollection` * sfc: `GeometryCollection`, unless the sfc is length 1, then the geometry as above * sf: `FeatureCollection` 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 ```r ## 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 SpatialPolygons class with precision agreement x_coord <- c( -114.345703125, -114.345703125, -106.61132812499999, -106.61132812499999, -114.345703125 ) y_coord <- c( 39.436192999314095, 43.45291889355468, 43.45291889355468, 39.436192999314095, 39.436192999314095 ) coords <- cbind(x_coord, y_coord) poly <- Polygon(coords) polys <- Polygons(list(poly), 1) sp_poly2 <- SpatialPolygons(list(polys)) geojson_list(sp_poly2, geometry = "polygon", precision = 4) geojson_list(sp_poly2, geometry = "polygon", precision = 3) geojson_list(sp_poly2, geometry = "polygon", precision = 2) # From SpatialPoints class with precision points <- SpatialPoints(cbind(x_coord, y_coord)) geojson_list(points) # 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 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 sf classes: if (require(sf)) { ## sfg (a single simple features geometry) p1 <- rbind(c(0, 0), c(1, 0), c(3, 2), c(2, 4), c(1, 4), c(0, 0)) poly <- rbind(c(1, 1), c(1, 2), c(2, 2), c(1, 1)) poly_sfg <- st_polygon(list(p1)) geojson_list(poly_sfg) ## sfc (a collection of geometries) p1 <- rbind(c(0, 0), c(1, 0), c(3, 2), c(2, 4), c(1, 4), c(0, 0)) p2 <- rbind(c(5, 5), c(5, 6), c(4, 5), c(5, 5)) poly_sfc <- st_sfc(st_polygon(list(p1)), st_polygon(list(p2))) geojson_list(poly_sfc) ## sf (collection of geometries with attributes) p1 <- rbind(c(0, 0), c(1, 0), c(3, 2), c(2, 4), c(1, 4), c(0, 0)) p2 <- rbind(c(5, 5), c(5, 6), c(4, 5), c(5, 5)) poly_sfc <- st_sfc(st_polygon(list(p1)), st_polygon(list(p2))) poly_sf <- st_sf(foo = c("a", "b"), bar = 1:2, poly_sfc) geojson_list(poly_sf) } ## End(Not run) ```

geojson_list function