frequency <- bind_rows(mutate(tidy_df %>%
                                filter(artist == 'Eminem'), author = 'Eminem'),
                       mutate(tidy_df %>%
                                filter(artist == 'Adele'), author = 'Adele'),
                       mutate(tidy_df %>%
                                filter(artist == 'Metallica'), author = 'Metallica')) %>%
  count(author, word) %>%
  group_by(author) %>%
  mutate(proportion = n/ sum(n)) %>%
  select(-n) %>%
  spread(author, proportion) %>%
  gather(author, proportion, `Eminem`:`Adele`)

library(scales)
ggplot(frequency, aes(x = proportion, y = `Metallica`, color = abs(`Metallica` - proportion))) +
  geom_abline(color = "gray40", lty = 2) +
  ggtitle("Figure 3: Different word choices") +
  geom_jitter(alpha = 0.1, size = 2.5, width = 0.3, height = 0.3) +
  geom_text(aes(label = word), check_overlap = TRUE, vjust = 1.5) +
  scale_x_log10(labels = percent_format()) +
  scale_y_log10(labels = percent_format()) +
  scale_color_gradient(limits = c(0, 0.001),
                       low = "darkslategray4", high = "gray75") +
  facet_wrap(~author, ncol = 2) +
  theme(legend.position = "none") +
  labs(y = 'Metallica', x = NULL)