```r
starwars %>%
  mutate(human = case_when(species == "Human" ~ "Human",
                           species != "Human" ~ "Not Human")) %>%
  filter(gender %in% c("female", "male"), !is.na(human)) %>%
  ggplot(aes(height, fill = gender)) +
  facet_grid(human ~ .) +
  geom_density()
```

```
## Warning: Removed 4 rows containing non-finite values (stat_density).
```

<img src="modern_R_files/figure-html/unnamed-chunk-421-1.png" width="672" />