jamesgrecian · January 27, 2026 09:35
diff --git a/map the atlantic.r b/map the atlantic.r
 #############################################
 ### Generate an enclosed map of the world ###
 #############################################

 # 2026-01-27
 # example script for Marie

 # this script creates a cookie cutter shape that overlays onto the map
 # helps to make final figures look a little prettier by hiding distortion in basemaps

 # load libraries
 library(tidyverse)
 library(rnaturalearth)
 library(sf)

 # Define a projection - in this case Lambert Azimuthal Equal Area centred on the mid Atlantic
 prj = "+proj=laea +lat_0=10 +lon_0=-20 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"

 # load a global shapefile
 world_shp <- rnaturalearth::ne_countries(scale = 50, returnclass = "sf")

 # define a box to clip shapefile to
 # this will be the spatial extent of the plot
 # make slightly bigger than required to avoid edge clip effects
 CP <- sf::st_bbox(c(xmin = -85, xmax = 40, ymin = -80, ymax = 80)) |>
  sf::st_as_sfc() |>
  sf::st_segmentize(1) |>
  st_set_crs(4326)

 # crop the shapefile
 world_shp <- world_shp |> 
  sf::st_crop(CP) |> 
  sf::st_buffer(0)

 # project the clipping polygon
 CP_prj <- CP |>
  st_transform(crs = prj)

 # get the bounding box in transformed coordinates and expand by 20%
 xlim <- st_bbox(CP_prj)[c("xmin", "xmax")]*1.2
 ylim <- st_bbox(CP_prj)[c("ymin", "ymax")]*1.2

 # create an enclosing rectangle to overlay on the map using bbox
 encl_rect <- 
  list(
    cbind(
      c(xlim[1], xlim[2], xlim[2], xlim[1], xlim[1]), 
      c(ylim[1], ylim[1], ylim[2], ylim[2], ylim[1])
    )
  ) |>
  st_polygon() |>
  st_sfc(crs = prj)

 # calcuate the difference between the enclosing rectangle and the CP outline
 # this becomes the cookie cutter that you overlay on your map
 cookie <- encl_rect |> st_difference(CP_prj)

 # example plot
 p1 <- ggplot() +
  theme_void(base_size = 8) +
  geom_sf(aes(), fill = "dark grey", colour = "dark grey", data = world_shp) +
  geom_sf(aes(), fill = "white", color = "black", data = cookie, size = .5) +
  coord_sf(xlim = c(-7000000, 7000000), ylim = c(-9750000, 8250000), crs = prj, expand = F)

 p1
	#############################################
	### Generate an enclosed map of the world ###
	#############################################

	# 2026-01-27
	# example script for Marie

	# this script creates a cookie cutter shape that overlays onto the map
	# helps to make final figures look a little prettier by hiding distortion in basemaps

	# load libraries
	library(tidyverse)
	library(rnaturalearth)
	library(sf)

	# Define a projection - in this case Lambert Azimuthal Equal Area centred on the mid Atlantic
	prj = "+proj=laea +lat_0=10 +lon_0=-20 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"

	# load a global shapefile
	world_shp <- rnaturalearth::ne_countries(scale = 50, returnclass = "sf")

	# define a box to clip shapefile to
	# this will be the spatial extent of the plot
	# make slightly bigger than required to avoid edge clip effects
	CP <- sf::st_bbox(c(xmin = -85, xmax = 40, ymin = -80, ymax = 80)) \|>
	sf::st_as_sfc() \|>
	sf::st_segmentize(1) \|>
	st_set_crs(4326)

	# crop the shapefile
	world_shp <- world_shp \|>
	sf::st_crop(CP) \|>
	sf::st_buffer(0)

	# project the clipping polygon
	CP_prj <- CP \|>
	st_transform(crs = prj)

	# get the bounding box in transformed coordinates and expand by 20%
	xlim <- st_bbox(CP_prj)[c("xmin", "xmax")]*1.2
	ylim <- st_bbox(CP_prj)[c("ymin", "ymax")]*1.2

	# create an enclosing rectangle to overlay on the map using bbox
	encl_rect <-
	list(
	cbind(
	c(xlim[1], xlim[2], xlim[2], xlim[1], xlim[1]),
	c(ylim[1], ylim[1], ylim[2], ylim[2], ylim[1])
	)
	) \|>
	st_polygon() \|>
	st_sfc(crs = prj)

	# calcuate the difference between the enclosing rectangle and the CP outline
	# this becomes the cookie cutter that you overlay on your map
	cookie <- encl_rect \|> st_difference(CP_prj)

	# example plot
	p1 <- ggplot() +
	theme_void(base_size = 8) +
	geom_sf(aes(), fill = "dark grey", colour = "dark grey", data = world_shp) +
	geom_sf(aes(), fill = "white", color = "black", data = cookie, size = .5) +
	coord_sf(xlim = c(-7000000, 7000000), ylim = c(-9750000, 8250000), crs = prj, expand = F)

	p1
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