How to place an inset map in R? There are many solutions out there using
the ggplot2 package (see Drawing beautiful maps programmatically with
R, sf and ggplot2
by Mel Moreno and Mathieu Basille). However, I like the old reliable plot
function, so the question is: is there another way?
There is. I found inspiration here and I just applied it to a map.
Required R packages
library(sf)
library(dplyr)
library(rnaturalearth)
Mimicking Moreno & Basille
I present here an alternative version of
Drawing beautiful maps programmatically with R, sf and ggplot2,
so the bulk of the detail can be found there. I focus only on the plot()
side.
world <- ne_countries(scale = "medium", returnclass = "sf")
USA <- subset(world, admin == "United States of America")
# Plot mainland USA----
par(mar = c(0, 0, 0, 0))
plot(
st_geometry(world %>%
st_transform(2163)),
xlim = c(-2500000, 2500000),
ylim = c(-2300000, 730000),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(2163),
col = "#FEFEE9",
border = "black",
add = T
)
# Plot Alaska----
plot(
st_geometry(world %>%
st_transform(3467)),
xlim = c(-2400000, 1600000),
ylim = c(200000, 2500000),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(3467),
col = "#FEFEE9",
border = "black",
add = T
)
# Plot Hawaii----
plot(
st_geometry(world %>%
st_transform(4135)),
xlim = c(-161, -154),
ylim = c(18, 23),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(4135),
col = "#FEFEE9",
border = "black",
add = T
)
Insetting
From now on, I focus on the inset part, using the fig argument of par().
Quoting statmethods:
(…) think of the full graph area as going from
(0,0)in the lower left corner to(1,1)in the upper right corner. The format of thefig=parameter is a numerical vector of the formc(x1, x2, y1, y2)(…)fig=starts a new plot, so to add to an existing plot usenew=TRUE.
With x1 and y1 as the starting points and x2, y2 as the final points,
we can set up those parameters and adjust the final placement of the insets.
Additionally, I added a box around the insets using bbox(). I didn’t mimic
Moreno & Basille here and I just worked it out by myself.
par(mar = c(0, 0, 0, 0))
plot(
st_geometry(world %>%
st_transform(2163)),
xlim = c(-2500000, 2500000),
ylim = c(-2300000, 730000),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(2163),
col = "#FEFEE9",
border = "black",
add = T
)
# Alaska
par(
fig = c(0.01, 0.28, 0.01, 0.33),
new = TRUE
)
plot(
st_geometry(world %>%
st_transform(3467)),
xlim = c(-2400000, 1600000),
ylim = c(200000, 2500000),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(3467),
col = "#FEFEE9",
border = "black",
add = T
)
box(which = "figure", lwd = 1)
# Hawaii
par(
fig = c(0.29, 0.45, 0.01, 0.15),
new = TRUE
)
plot(
st_geometry(world %>%
st_transform(4135)),
xlim = c(-161, -154),
ylim = c(18, 23),
col = "#F6E1B9",
border = "#646464",
bg = "#C6ECFF"
)
plot(
st_geometry(USA) %>% st_transform(4135),
col = "#FEFEE9",
border = "black",
add = T
)
box(which = "figure", lwd = 1)
Results may vary depending on the size of the original plot (Mainland USA), your plotting device and the output. However, with a bit of trial and error, it is quite easy to adjust the final result.
As an example, see one of my contributions to Wikimedia Commons, which represents a map of the NUTS3 regions of the European Union. Several countries (France, Portugal, Spain) have overseas territories, so I made a few insets on the right side.
