I am trying to create a list that is correctly formatted as topoJSON from an sf object.
What would work when reading a valid topoJSON file is:
sa <- jsonlite::read_json("https://raw.githubusercontent.com/pachadotdev/d3po/main/dev/south-america.topojson", simplifyVector = F)
What I am trying to do is:
# install_github("pachadotdev/canadamaps")
library(canadamaps)
library(sf)
library(geojsonio)
provinces <- get_provinces()
provinces <- st_as_sf(provinces)
geojson_write(provinces, file = "provinces.geojson")
provinces2 <- geojson_read("provinces.geojson")
geo2topo(provinces)
Error: no 'geo2topo' method for sftbl_dftbldata.frame
Is there any option to convert to topoJSON from R?
I tried saving as geoJSON and then re-exporting in QGIS, but it doesn't save as topoJSON.
geo2topo works on JSON strings, not R objects.
Start with the geoJSON file you wrote in your example. ogrinfo tells me its geoJSON:
$ ogrinfo provinces.geojson
INFO: Open of `provinces.geojson'
using driver `GeoJSON' successful.
1: provinces (Multi Polygon)
Read it into R as text - this is the plain text geoJSON:
> s = readLines("provinces.geojson")
Warning message:
In readLines("provinces.geojson") :
incomplete final line found on 'provinces.geojson'
> substr(s, 1, 100)
[1] "{\"type\":\"FeatureCollection\",\"features\":[{\"type\":\"Feature\",\"properties\":{\"pruid\":46,\"prname\":\"Manitob"
Now convert to topoJSON string:
> tj = geojsonio::geo2topo(s)
> substr(tj, 1, 100)
{"type":"Topology","objects":{"foo":{"type":"GeometryCollection","geometries":[{"type":"MultiPolygon
and write text to file:
> writeLines(tj, "tj.topojson")
>
Giving what gdal interprets as topoJSON:
$ ogrinfo tj.topojson
INFO: Open of `tj.topojson'
using driver `TopoJSON' successful.
1: foo (Multi Polygon)
I'm not sure where it gets the foo layer name from, this can probably be set to something else somewhere, unless its actually in the data...