Generate a state map using choroplethr and add custom-formatted labels.

choroplethr_format_labels.R

c = StateChoropleth$new(df_state_demographics)
c$title  = "Population by State, Percent Black"
c$set_num_colors(7)
c$show_labels = F

df_state_labels = data.frame(long = state.center$x, lat =
state.center$y, name=tolower(state.name), label = state.abb)
df_state_labels = df_state_labels[!df_state_labels$name %in% c("alaska",
"hawaii"), ]

d <-c$render() + 
      geom_text(data = df_state_labels, 
                aes(long, lat, label = label, group = NULL),
                color = gray(.1), size=4)

print(d)