Demonstration of how to overlay one region onto another using R and sf

sf_map_overlay.R

library(sf)
library(ggplot2)

# Data from https://www.geoboundaries.org/index.html#getdata
de2 <- read_sf("data/geoBoundaries-DEU-ADM2-all/geoBoundaries-DEU-ADM2_simplified.shp")

# Extract Munich and Berlin to separate objects
munich <- dplyr::filter(de2, DistrictCo == "09162")
berlin <- dplyr::filter(de2, DistrictCo == "11000")

# Find the centroids of each city
berlin_centre <- berlin |>
  st_centroid() |> 
  st_geometry()

munich_centre <- munich |>
  st_centroid() |> 
  st_geometry()

# Use the centroids to calculate the shift required
# to move Munich to the centre of Berlin
coord_shift <- (berlin_centre - munich_centre)

# Make a new Munich shifted up to Berlin
# The CRS goes missing and needs to be specified again
munich_overlay <- munich
st_geometry(munich_overlay) <- st_geometry(munich_overlay) + coord_shift
st_crs(munich_overlay) <- "EPSG:4326"

# Plot
ggplot() +
  geom_sf(data = berlin, colour = "#377EB8") +
  geom_sf(data = munich_overlay, colour = "#E41A1C") +
  coord_sf() +
  theme_minimal() +
  labs(
    title = "How does <span style='color:#E41A1C;'>Munich</span> compare to <span style='color:#377EB8;'>Berlin</span>?",
    caption = "Map data: www.geoboundaries.org\nVisualisation: github.com/edonnachie"
  ) +
  theme(plot.title = ggtext::element_markdown(size = 12))

ggsave(filename = "berlin_munich.png",
       type = "cairo", bg = "white",
       width = 10, height = 10, units = "cm", dpi = 300)