Open and merge multiple shapefiles

March 27, 2019
By

(This article was first published on r.iresmi.net, and kindly contributed to R-bloggers)

or more precisely union many spatial tables in R in a tidy way.

  • dplyr::bind_rows doesn’t work on sf objects ;
  • base::rbind only work on two tables and so that’s not straightforward to use*.

So we’ll use purrr::map and tidyr::unnest.

First get some data, the communes of three french départements :

library(tidyverse)
library(sf)
library(fs)
library(httr)
library(leaflet)

# https://fr.actualitix.com/blog/shapefiles-des-departements-de-france.html

url <-  c("https://fr.actualitix.com/blog/actgeoshap/01-Ain.zip",
          "https://fr.actualitix.com/blog/actgeoshap/73-savoie.zip",
          "https://fr.actualitix.com/blog/actgeoshap/74-haute-savoie.zip")

dep <- str_extract(url, "\\d{2}.*$")

list(url, dep) %>% 
  pwalk(~ GET(.x, write_disk(.y)))

walk(dep, unzip, junkpaths = TRUE, exdir = "shp")

We can then create a 3 rows data frame containing a list-column in which we store the sf object. Then we just unnest it. This operation erases the sf-class, we have to add it back.

res <- dir_ls("shp", glob = "*.shp") %>% 
  tibble(fname = .) %>%
  mutate(data = map(fname, read_sf)) %>%
  unnest(data) %>%
  st_as_sf() %>%
  st_set_crs(2154)

write_sf(res, "shp/3dep.shp")

res %>% 
  st_transform(4326) %>% 
  leaflet() %>%
    addPolygons() %>% 
    addTiles()

Bonus : we have the source filename stored in the resulting shapefile.

* We could have used

dir_ls("shp", glob = "*.shp") %>% 
  map(read_sf) %>%
  do.call(rbind, .)

but the column structure doesn’t match here…

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