You want to remove background elements from a map.

First, save the following theme:

# Create a theme with many of the background elements removed
theme_clean <- function(base_size = 12) {
require(grid) # Needed for unit() function
  theme_grey(base_size) %+replace%
  theme(
    axis.title        = element_blank(),
    axis.text         = element_blank(),
    panel.background  = element_blank(),
    panel.grid        = element_blank(),
    axis.ticks.length = unit(0, "cm"),
    axis.ticks.margin = unit(0, "cm"),
    panel.margin      = unit(0, "lines"),
    plot.margin       = unit(c(0, 0, 0, 0), "lines"),
    complete = TRUE
  )
}

Then add it to the map (Figure 13-38). In this example, we’ll add it to one of the choropleths we created in Creating a Choropleth Map: