How to fix axis and add polygon to inset map in ggplot2 - r

Question

I'm trying to add a couple details to my map in ggplot2 but I'm new to the package and I'm not sure how to proceed. Code and map are below (ignore the weird spacing on the map, I took a screen shot in Rstudio). Thanks for taking a look!
I'm trying to do the following:
Add latitude and longitude tick marks on the x and y axis. I coded it in the script below but nothing is happening, not sure why - no errors pop up.
If possible, I'd like to add a box in the inset map showing the extent/coverage of the larger map, since the points in the smaller map (the red ones) are barely visible. I'm not sure how to add and place a polygon in the inset map.
Here is what the map currently looks like for reference:
library(raster)
library(ggplot2)
library(ggthemes)
library(ggsn)
library(ggmap)
library(maps)
library(mapdata)
mapdata <- getData("GADM", country = "panama", level = 1)
mymap <- fortify(mapdata)
mypoint <- data.frame(long=c(-79.743, -79.696, -79.645, -79.595),
lat=c(9.160, 9.117, 9.058, 9.015),
group=c("L", "GW", "OGR", "LC"))
mypoint2 <- data.frame(long=c(-79.846, -79.707, -79.665, -79.610),
lat=c(9.181, 9.112, 9.057, 9.014),
group=c("BCI", "G", "EH", "MF"))
g1 <- ggplot() +
geom_blank(data = mymap, aes(x=long, y=lat)) +
geom_map(data = mymap, map = mymap,
aes(group = group, map_id = id),
fill = "#b2b2b2", color = "black", size = 0.3) +
coord_sf(xlim=c(-80,-79.5), ylim=c(8.9, 9.25), expand = FALSE) +
geom_point(data = mypoint, aes(x = long, y = lat),
color = "black", size = 3) +
geom_label(data = mypoint, aes(label = group, x = long, y = lat),
size = 3, fontface = "bold", nudge_x = c(0.015, 0.02, 0.022, 0.018)) +
geom_point(data = mypoint2, aes(x = long, y = lat),
color = "blue", size = 3) +
geom_label(data = mypoint2, aes(label = group, x = long, y = lat),
size = 3, fontface = "bold", nudge_x = c(-0.02, -0.018, -0.02, -0.02)) +
scale_x_continuous(limits = c(-80,-79.5), expand = c(0, 0)) +
scale_y_continuous(limits = c(8.9, 9.25), expand = c(0, 0)) +
theme_map() +
ggsn::scalebar(location = "bottomleft", dist = 5,
transform = TRUE, dist_unit = "km", model = 'WGS84',
x.min = -79.97, x.max = -79.8,
y.min = 8.93, y.max = 9.25) +
north(x.min = -79.6, x.max = -79.5,
y.min = 9.2, y.max = 9.24,
location = "toprgiht", scale = 0.1)
g2 <- ggplotGrob(
ggplot() +
geom_polygon(data = mymap,
aes(x = long, y = lat, group = group),
fill = "#b2b2b2", color = "black", size = 0.3) +
geom_point(data = mypoint, aes(x = long, y = lat),
color = "red", size = 0.5) +
coord_map("polyconic") +
theme_map() +
theme(panel.background = element_rect(fill = NULL))
)
g3 <- g1 +
annotation_custom(grob = g2, xmin = -79.75, xmax = -79.51,
ymin = 8.9, ymax = 9.0)
g3

Answer 1

Latitude and longitude tick marks are disappearing because of theme_map() - it sets axis_ticks and axis_text (among other things) to element_blank(). One way to get them back is to override theme_map() with
g1_with_lbls <- g1 +
theme(
axis.text = element_text(),
axis.ticks = element_line(),
axis.title = element_text()
) +
xlab("Longitude") +
ylab("Lattitude")
You would place the polygon on the smaller map as a part of the ggplotGrob object you are creating
g2 <- ggplotGrob(
ggplot() +
geom_polygon(data = mymap,
aes(x = long, y = lat, group = group),
fill = "#b2b2b2", color = "black", size = 0.3) +
geom_point(data = mypoint, aes(x = long, y = lat),
color = "red", size = 0.5) +
coord_map("polyconic") +
theme_map() +
theme(
panel.background = element_rect(fill = NULL)
) +
geom_rect(
aes(xmin = -80, xmax = -79, ymin = 8.5, ymax = 9.5), fill = NA,
col = "red", size = 1
)
)
Then
g3 <- g1_with_lbls +
annotation_custom(grob = g2, xmin = -79.75, xmax = -79.51,
ymin = 8.9, ymax = 9.0)
g3
Has both the ticks and the rectangle.