I want to import data as an sf object in R from a leaflet map. The map is this site: https://erickgn.github.io/mapafc/ I also have the HTML from the map as following:https://raw.githubusercontent.com/erickgn/mapafc/main/index.html.
1 Answer
I also have the HTML from the map as following:https://raw.githubusercontent.com/erickgn/mapafc/main/index.html.
Then you have everything. Either save the page locally, either scrape it using xml2
package. If you look on the page source, you can find something like:
geo_json_b75320e180b34bb88a8a9025dff8675e_add({"bbox": [-44.447264,
-23.03329, -41.6957233, -22.2949485],[...]
as seems that are your features, you can read it with sf::st_read or jsonlite
package.
A small example for the first JSON:
library(rvest)
url <- "https://raw.githubusercontent.com/erickgn/mapafc/main/index.html"
text <- html_text(read_html(url))
Now we have to locate two strings which are before and after json and
take the part between. Please note +1, -22
-- the first one is quite obvious, the second one is a bit of trying to remove unnecessary new lines etc.
library(stringi)
st <- stri_locate_first_fixed(text, "geo_json_b75320e180b34bb88a8a9025dff8675e_add(")[2]+1
fi <- stri_locate_first_fixed(text, "geo_json_b75320e180b34bb88a8a9025dff8675e.bindTooltip(")[1]-22
json <- substring(text, st, fi)
And finally let's convert json to R objects:
jsonlite::fromJSON(json)
#> $bbox
#> [1] -44.44726 -23.03329 -41.69572 -22.29495
#>
#> $features
#> bbox
#> 1 -43.59792, -22.82906, -43.58869, -22.82160
#> 2 -43.38023, -22.96123, -43.37173, -22.95453
#> 3 -43.50182, -23.03329, -43.49279, -23.02227
#> 4 -43.29931, -22.99099, -43.29163, -22.98606
[...]
You can repeat similar steps for next json(s).
And reading with sf
package:
library(sf)
a <- st_read(json)
#> Reading layer `OGRGeoJSON' from data source
#> [...]
#> using driver `GeoJSON'
#> Simple feature collection with 249 features and 16 fields
#> Geometry type: POLYGON
#> Dimension: XY
#> Bounding box: xmin: -44.44726 ymin: -23.03329 xmax: -41.69572 ymax: -22.29495
#> Geodetic CRS: WGS 84
plot(a$geometry)
Regards, Grzegorz
-
1I had done something like this but in the end I got an error #Url url <- "raw.githubusercontent.com/erickgn/mapafc/main/index.html" #Open html pjs_session$go(url) rendered_source <- pjs_session$getSource() html_document <- read_html(rendered_source) text <- html_document %>% html_node(xpath = '/html/body/pre') %>% html_text() myMap <- FROM_GeoJson(url_file_string = text) Commented Feb 15, 2022 at 20:18
-
2Hi @MariaMittelbach, please have a look on my extended answer above. Commented Feb 15, 2022 at 21:41