Mapping state borders with ggplot

Question

I am attempting to create a ggplot map with both county and state boundaries. I am able to produce the map with county boundaries, but when adding the following line to get state borders as well, I run into an issue. The code is reproduced below.

ggplot2::geom_polygon(aes(x= long, y = lat, group = group), fill = NA, color = "black",

                      data = filter(us_map(), abbr %in% states_of_interest))

When I run this code, I get the error:

"Error in FUN(X[[i]], ...)

object 'long' not found". I am relatively unfamiliar with the us_map package, but I was told using long at lat for x and y would function correctly.

I have tried adding the command

"inherit.aes = FALSE"

upon other stack overflow post recommendations, but it did not solve the error.

Answer 1

The us_map function returns an object with x and y for lat/long. You can store the counties and states separately, then add them both to ggplot as polygons.

library(usmap)

states_of_interest <- c("CA","OR", "WA")

counties <- us_map(regions = "counties", include = states_of_interest)
states <- us_map(include = states_of_interest)

ggplot() +
  geom_polygon(data = counties, aes(x = x, y = y, group = group), fill = NA, color = "black") +
  geom_polygon(data = states, aes(x = x, y = y, group = group), fill = NA, color = "red") +
  coord_equal()