Adding County Names to Map in maps package

[uvictori]

Hello,

I am trying to create a map of Michigan with some particular counties highlighted. Which I have done so here:

The code I'm working with is:
#create Michigan map

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

states <- map_data("state")
michigan <- subset(states, region= "michigan")
mi_df <- subset(states, region == "michigan")
counties <- map_data("county")
mi_county <- subset(counties, region == "michigan")
mi_study_counties<- subset(mi_county, subregion %in% c("chippewa", "cheboygan", "delta", "schoolcraft", "otsego", "menominee"))

mi_base <- ggplot(data = mi_df, mapping = aes(x = long, y = lat, group = group)) +
coord_fixed(1.3) +
geom_polygon(color = "black", fill="white")+
theme_void()
mi_base

mi_base+ geom_polygon(data = mi_study_counties, fill = "gray", color = "black") +
geom_polygon(color = "black", fill = NA)

What I need help with is labeling the county names on the counties that I have highlighted. Also, is there a way to do a fill of different colors for the different counties? Like fill 3 of them gray and 3 of them blue? Any help is greatly appreciated!

[mfherman]

If you're interested in dipping your toe into a new spatial paradigm in R, I would highly recommend looking into the sf package. It integrates very well with plotting in ggplot, leaftlet, mapview, and other spatial packages in R.

Below is a worked example of getting state and county sf data from the tigris package and then using ggplot2 to make and label the map. FYI: I used the ggsflabel package for the labels and it is only on github for now. If you need CRAN packages only, you can simply replace geom_sf_label_repel() with geom_sf_label() which is part of ggplot2.

library(ggplot2)
library(dplyr, warn.conflicts = FALSE)
library(ggsflabel, warn.conflicts = FALSE)
library(tigris, warn.conflicts = FALSE)

mi_state <- states(cb = TRUE, class = "sf") %>% 
  filter(NAME == "Michigan")

mi_county <- counties(state = "MI", cb = TRUE, class = "sf")

mi_study_counties <- mi_county %>% 
  filter(NAME %in% c("Chippewa", "Cheboygan", "Delta",
                     "Schoolcraft", "Otsego", "Menominee"))

mi_study_counties %>% 
  ggplot() +
  geom_sf(fill = "gray") +
  geom_sf(data = mi_state, fill = NA) +
  geom_sf_label_repel(aes(label = NAME), force = 50) +
  theme_void()

^{Created on 2020-03-04 by the reprex package (v0.3.0)}

[uvictori]

This is perfect! Thank you. Any idea on putting colors for specific counties? I need Delta, Schoolcraft, and Chippewa Counties to be one color, and Menominee, Cheboygan, and Otsego Counties to be another color.

[mfherman]

Sure thing! One easy way is to define the colors in the data frame you send into ggplot() and the use scale_fill_identity() to use those colors for fill.

library(ggplot2)
library(dplyr, warn.conflicts = FALSE)
library(ggsflabel, warn.conflicts = FALSE)
library(tigris, warn.conflicts = FALSE)

mi_state <- states(cb = TRUE, class = "sf") %>% 
  filter(NAME == "Michigan")

mi_county <- counties(state = "MI", cb = TRUE, class = "sf")

mi_study_counties <- mi_county %>% 
  filter(NAME %in% c("Chippewa", "Cheboygan", "Delta",
                     "Schoolcraft", "Otsego", "Menominee")) %>% 
  mutate(fill_color = if_else(NAME %in% c("Chippewa", "Delta", "Schoolcraft"),
                              "steelblue", "coral")
         )

mi_study_counties %>% 
  ggplot() +
  geom_sf(aes(fill = fill_color)) +
  geom_sf(data = mi_state, fill = NA) +
  geom_sf_label_repel(aes(label = NAME), size = 3, force = 50) +
  scale_fill_identity() +
  theme_void()

^{Created on 2020-03-04 by the reprex package (v0.3.0)}