Write TopoJSON from various inputs
topojson_write(
input,
lat = NULL,
lon = NULL,
geometry = "point",
group = NULL,
file = "myfile.topojson",
overwrite = TRUE,
precision = NULL,
convert_wgs84 = FALSE,
crs = NULL,
object_name = "foo",
quantization = 0,
...
)A topojson_write class, with two elements:
path: path to the file with the TopoJSON
type: type of object the TopoJSON came from, e.g., SpatialPoints
Input list, data.frame, spatial class, or sf class.
Inputs can also be dplyr tbl_df class since it inherits
from data.frame
(character) Latitude name. The default is NULL, and we
attempt to guess.
(character) Longitude name. The default is NULL, and we
attempt to guess.
(character) One of point (Default) or polygon.
(character) A grouping variable to perform grouping for polygons - doesn't apply for points
(character) A path and file name (e.g., myfile), with the
.geojson file extension. Default writes to current working
directory.
(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.
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).
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.
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.
(character) name to give to the TopoJSON object created. Default: "foo"
(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
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().
Under the hood we simply wrap geojson_write(), then
take the GeoJSON output of that operation, then convert to TopoJSON with
geo2topo(), then write to disk.
Unfortunately, this process requires a number of round trips to disk, so speed ups will hopefully come soon.
Any intermediate geojson files are cleaned up (deleted).
geojson_write(), topojson_read()