number of borders.R

library(tidyverse)
library(sf)
library(spdep)
library(rnaturalearth)
names <- ne_countries() %>% 
  st_as_sf() %>% 
  st_drop_geometry() %>% 
  pull(name)
mat <- ne_countries() %>% 
  st_as_sf() %>% 
  poly2nb() %>% 
  nb2mat(zero.policy = T,style = "B")
colnames(mat) <- rownames(mat) <- names
as_tibble(mat) %>% 
  mutate(from = names) %>% 
  gather(to, connection,-from) %>% 
  group_by(to) %>% 
  summarise(n = sum(connection)) %>% 
  arrange(-n) %>% 
  left_join(ne_countries() %>% 
              st_as_sf(), by = c("to"= "name")) %>% 
  st_as_sf() %>% 
  mutate(n = ifelse(is.na(n),0,n)) %>% 
  ggplot(aes(fill = n)) + 
  geom_sf() + 
  labs(title = "Number of land borders") + 
  scale_fill_continuous(high = "#132B43", low = "#56B1F7")