How to add state abbreviations to a map in R

Question

I am attempting to add a layer with state abbreviations to this map:

US Map-- user locations represented by heat plot; no state name abbreviations

I have a list of users from a suvery whose self-reported location I mapped to determine the most popular states. I would like to add a "layer" to this map with state abbreviations.

This is an example of the dataset I'm using. I have a column with the state abbreviations, I just don't know how to layer them on top of the map. Btw I am using library(usmap).

state	stateabbr	n	fips
Alabama	AL	1	01
Arkansas	AR	1	05
California	CA	32	06
Florida	FL	19	12

Lastly, the code for the map:

usmap3 <- plot_usmap(data = statecounts, regions = "state", values = "n") +
 scale_fill_gradientn(name = "Count", colours = myPalette(100)) +
  labs(title = "Frequency of Unique Users in the United States",
       caption = "",
       fill = "Count")
usmap3

Answer 1

One simple option would be to use the labels argument of plot_usmap which will automatically add labels with state abbreviations for all states.

In case that you want only some states to be labelled then you could first get the coordinates of the state centroids which are available via usmapdata::centroid_labels("states") and join these coordinates to your dataset. Afterwards you could add the state abbreviations to your map via geom_text like so:

library(usmap)
library(ggplot2)

# Get centroids
centroid_labels <- usmapdata::centroid_labels("states")

# Join centroids to data
state_labels <- merge(statecounts, centroid_labels, by = "fips")

plot_usmap(data = statecounts, regions = "state", values = "n") +
  geom_text(data = state_labels, aes(
    x = x, y = y,
    label = stateabbr,
  ), color = "white") +
  labs(title = "Frequency of Unique Users in the United States",
       caption = "",
       fill = "Count")

DATA

statecounts <- data.frame(
  stringsAsFactors = FALSE,
             state = c("Alabama", "Arkansas", "California", "Florida"),
         stateabbr = c("AL", "AR", "CA", "FL"),
                 n = c(1L, 1L, 32L, 19L),
              fips = c("01", "05", "06", "12")
  )