# Convert many input types with spatial data to TopoJSON as a list ```r topojson_list( input, lat = NULL, lon = NULL, group = NULL, geometry = "point", type = "FeatureCollection", convert_wgs84 = FALSE, crs = NULL, object_name = "foo", quantization = 0, ... ) ``` ## 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. - `object_name`: (character) name to give to the TopoJSON object created. Default: "foo" - `quantization`: (numeric) quantization parameter, use this to quantize geometry prior to computing topology. Typical values are powers of ten (`1e4`, `1e5`, ...), default is `0` to not perform quantization. For more information about quantization, see this by Mike Bostock https://stackoverflow.com/questions/18900022/topojson-quantization-vs-simplification/18921214#18921214 - `...`: args passed down through `topojson_json()` to `geojson_json()`; see `geojson_json()` for help on what's supported here ## Returns a list with TopoJSON ## Details Internally, we call `topojson_json()`, then use an internal function to convert that JSON output to a list The `type` parameter is automatically converted to `type="auto"` if a sf, sfc, or sfg class is passed to `input` ## Examples ```r ## Not run: # From a numeric vector of length 2 to a point vec <- c(-99.74, 32.45) topojson_list(vec) # Lists ## From a list mylist <- list( list(latitude = 30, longitude = 120, marker = "red"), list(latitude = 30, longitude = 130, marker = "blue") ) topojson_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)) topojson_list(vecs, geometry = "polygon") # from data.frame to points (res <- topojson_list(us_cities[1:2, ], lat = "lat", lon = "long")) as.json(res) ## guess lat/long columns topojson_list(us_cities[1:2, ]) topojson_list(states[1:3, ]) topojson_list(states[1:351, ], geometry = "polygon", group = "group") topojson_list(canada_cities[1:30, ]) # from data.frame to polygons head(states) topojson_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) topojson_list(sp_poly) # From SpatialPolygonsDataFrame class sp_polydf <- as(sp_poly, "SpatialPolygonsDataFrame") topojson_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)) topojson_list(s) # From SpatialPointsDataFrame class s <- SpatialPointsDataFrame(cbind(x, y), mtcars[1:5, ]) topojson_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)) topojson_list(sl1) topojson_list(sl12) as.json(topojson_list(sl12)) as.json(topojson_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) topojson_list(sldf) as.json(topojson_list(sldf)) as.json(topojson_list(sldf), pretty = TRUE) # From SpatialGrid x <- GridTopology(c(0, 0), c(1, 1), c(5, 5)) y <- SpatialGrid(x) topojson_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)) topojson_list(sgdf) # From SpatialPixels library("sp") pixels <- suppressWarnings(SpatialPixels(SpatialPoints(us_cities[c("long", "lat")]))) summary(pixels) topojson_list(pixels) # From SpatialPixelsDataFrame library("sp") pixelsdf <- suppressWarnings( SpatialPixelsDataFrame(points = canada_cities[c("long", "lat")], data = canada_cities) ) topojson_list(pixelsdf) ## End(Not run) # 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)) topojson_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))) topojson_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) topojson_list(poly_sf) } ```

topojson_list function