制作突出显示R中特定县和点的州图（ggmaps，maps，ggplot2）

Question

I am trying to build a map of state, that has its counties outlined, and one county colored in blue with a point for a specific resort. Alas, I am having trouble getting a county colored or adding a specific point. My code builds off of http://eriqande.github.io/rep-res-web/lectures/making-maps-with-R.html Thank you for any insights!

library(ggplot2)
library(ggmap)
library(maps)
library(mapdata)    

states <- map_data("state")
dim(states)
ut_df <- subset(states, region == "utah")
head(ut_df)

counties <- map_data("county")
ut_county <- subset(counties, region == "utah")
head(ut_county)

ut_base <- ggplot(data = ut_df, mapping = aes(x = long, y = lat, group = 
group)) +
coord_fixed(1.3) +
geom_polygon(color = "black", fill = "gray")

ut_base + theme_nothing() +
geom_polygon(data = ut_county, fill = NA, color = "white") +
geom_polygon(color = "black", fill = NA)  # get the state border back on top

Answer 1

# Select a subregion
single_county <- subset(ut_county, subregion=="utah")

# Fill the selected subregion with a predefined color and
# plot a colored point with a specified long. and lat.
ut_base + theme_void() +
geom_polygon(data = ut_county, fill = NA, color = "white") +
geom_polygon(color = "black", fill = NA) +
geom_polygon(data = single_county, fill = "red", color = "white") +
geom_point(x=-111.8, y=40.2, col="blue", size=3)