library(ggmapinset)
#> Loading required package: sf
#> Linking to GEOS 3.11.2, GDAL 3.6.4, PROJ 9.2.0; sf_use_s2() is TRUE
library(ggplot2)
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
This article provides some recipes for working with insets.
Different aesthetics for inset layer
By default, geom_sf_inset() creates two copies of the
map layer: one for the base map and the other for the inset map. The
inset is transformed and clipped, but uses the same underlying
aesthetics mapping and parameters.
If you want to have different aesthetics for the two layers, you’ll
need to turn off this copying with map_base = "none". With
this parameter set and an inset parameter provided, only
the inset layer will be drawn. To draw only the base layer, you can use
map_inset = "none", inset = NULL, or simply
use the normal geom_sf().
ggplot(nc) +
# this is equivalent to the following line:
# geom_sf_inset(fill = "white", map_inset = "none") +
geom_sf(fill = "white") +
geom_sf_inset(aes(fill = AREA), map_base = "none") +
geom_inset_frame() +
coord_sf_inset(inset = configure_inset(
centre = sf::st_centroid(sf::st_geometry(nc)[nc$NAME == "Bladen"]), scale = 1.5,
translation = c(-180, -50), radius = 50, units = "mi"))
Inset frame backgrounds
By default, the inset frame is transparent, although often it makes
sense to add a solid background so that the inset is distinguishable
from any overlapping part of the base map. The aesthetics of the two
parts of the frame and the burst lines connecting them can be controlled
separately.
Note that when the background is filled, we need to specify the base
and inset maps in separate layers so that the frame can slip in between
them.
ggplot(nc) +
geom_sf(aes(fill = AREA)) +
geom_inset_frame(target.aes = list(fill = "white")) +
geom_sf_inset(aes(fill = AREA), map_base = "none") +
coord_sf_inset(inset = configure_inset(
centre = st_centroid(st_geometry(nc)[nc$NAME == "Yancey"]), scale = 2,
translation = c(100, -120), radius = 50, units = "mi"))
Multiple insets
For multiple insets, the appropriate inset configuration just needs
to be passed to each layer separately. It’s probably clearer to avoid
providing an inset to the coordinate system in this case.
Since the inset-aware layers will duplicate themselves for the base
and inset maps, you will probably want to disable that behaviour with
map_base = "none" to avoid having multiple identical copies
of the base map.
inset1 <- configure_inset(
centre = sf::st_centroid(sf::st_geometry(nc)[nc$NAME == "Bladen"]), scale = 1.5,
translation = c(150, -50), radius = 50, units = "mi")
inset2 <- configure_inset(
centre = sf::st_centroid(sf::st_geometry(nc)[nc$NAME == "Orange"]), scale = 3,
translation = c(30, 120), radius = 30, units = "mi")
ggplot(nc) +
# base map
geom_sf_inset() +
# inset 1
geom_sf_inset(map_base = "none", inset = inset1) +
geom_inset_frame(inset = inset1, colour = "red") +
# inset 2
geom_sf_inset(map_base = "none", inset = inset2) +
geom_inset_frame(inset = inset2, colour = "blue")
