Overlapping shp maps in sf

0
votes

I have two shapefiles that I read into R with sf.

  • The first shp file covers regions.
  • The second shp file covers administrative districts.
  • The electoral districts are nested into regions.

I would like to overlay the two maps, then coloring each electoral district in a shade of the same color, having one color for each region.

I can plot the two and play around with colors but cannot overlay and coloring.

Files can be accessed here from the Italian National Institute of Statistics : Reg1991_WGS84.shp: http://www.istat.it/storage/cartografia/confini_amministrativi/non_generalizzati/Limiti1991.zip CAMERA_PLURI_2017.shp: https://www.istat.it/storage/COLLEGI_ELETTORALI_2017.zip

library(sf)

italia_regions_1991<- read_sf("Limiti1991/Reg1991/Reg1991_WGS84.shp")  %>% select(geometry)
italia_camera_pluri <- read_sf("COLLEGI_ELETTORALI_2017/CAMERA_PLURI_2017.shp") %>% select(geometry)
2
rggplot2shapefilesf

2 Answers

0
votes

Consider intersecting the regions & districts via sf::st_intersection - note however that there seems to be some overlap, as the regions and districts do not align perfectly (they mostly do, but not quite...)

I have also transformed the CRS to WGS84; perhaps not necessary, but works better with leaflet and the like...

library(sf)
library(dplyr)
library(ggplot2)

italia_regions_1991<- read_sf("Reg1991_WGS84.shp") %>% 
  select(region = DEN_REG) %>% # this, and geometry by default
  st_transform(4326)

italia_camera_pluri <- read_sf("CAMERA_PLURI_2017.shp") %>% 
  select(geometry) %>% # only geometry...
  st_transform(4326) 

result <- italia_camera_pluri %>% 
  st_intersection(italia_regions_1991) 

ggplot(data = result, aes(fill = region)) +
  geom_sf()

enter image description here

3
votes

This will get you started....

I used the leafgl library, since you are plotting alot of polylines/plygons... This performs (pretty)fast...

library(sf)
library(devtools)
library(leaflet)
#install leaflet with gl-suport
devtools::install_github("r-spatial/leafgl")
library(leafgl)
library(colourvalues)


#read shapefile regions and cast to polygons
sf1 <- st_read( "e:/two_shapes/Limiti1991/Reg1991/Reg1991_WGS84.shp" ) %>% st_cast( "POLYGON", warn = FALSE )
#read shapefile and cast to POLYGON and then to LINESTRING
sf2 <- st_read( "e:/two_shapes/COLLEGI_ELETTORALI_2017/COLLEGI_ELETTORALI_2017.shp") %>%
  st_cast( "POLYGON", warn = FALSE ) %>%
  st_cast( "LINESTRING", warn = FALSE )

#creaae color matrix for the regions( depending om DEN_REG), and for the polylines (=black)
col_region <- colour_values_rgb(sf1$DEN_REG, include_alpha = FALSE) / 255
col_lines  <- matrix(data = c(0,0,0), nrow = 1 )

#plot leaflet (takes some time)
leaflet() %>% addTiles() %>%
  addGlPolygons(data = sf1, color = col_region) %>%
  addGlPolylines( data = sf2, color = col_lines)

result

enter image description here