I've made a faceted a box plot using two variables. How can I put headers for the facet?
library(ggplot2)
ggplot(data = data60 ,aes(x = education_level, y = lw)) +
geom_boxplot() +
facet_grid(rns~smsa) +
labs(x = "Education Level", y = "Log Wage") +
theme_bw()