Customizing choropleths in R

choroplot.R

### Load libraries
library(ggplot2)

### Load data
dat <- read.csv("choroData.csv")

### Set up the bare plot
p <- ggplot(data = dat,
       aes(x = long, y = lat, group = group,
           fill = factor(Voucher.count.June.2019)))

### Add on the state boundaries
p <- p + 
    geom_polygon()

### Paint state borders in white
p <- p + 
    geom_path(colour = "white")

### Chang the fill type (continuous -> discrete) and fill legend
p <- p +
    scale_fill_grey("Voucher count\n(June 2019)")

### Set the text elements to be bigger
### (You can use a bigger number than 18)
p <- p +
    theme_grey(base_size = 18,
               base_family = "serif")

### Set the background to white
p <- p +
    theme(panel.background = element_rect(fill = "white"))

### Remove axes
p <- p +
    theme(axis.title.x = element_blank(),
          axis.title.y = element_blank(),
          axis.text.x = element_blank(),
          axis.text.y = element_blank(),
          axis.ticks = element_blank())