Add Points to Choropleth Map in ggplot2

Question

I\'m looking at the following example from Hadley Wickham\'s ggplot2:

library(ggplot2)
library(maps)
states<-map_data(\"state\")
arrests<-         


        

Answer 1

This seems to work just fine for me:

base_map + 
    geom_point(aes(long, lat,fill = NULL,group = NULL), size = 1,data=us.cities) + 
    borders("state", size=.5)

Although you may want to exclude the cities in HI and AK, as I did to produce this version of the plot: