bar <- ggplot(data = diamonds, mapping = aes(x = cut, fill = cut)) +
```
geom_bar( show.legend = FALSE, width = 1 ) +
theme(aspect.ratio = 1) +
## Coordinate systems challenges
labs(x = NULL, y = NULL)
- Turn a stacked bar chart into a pie chart using `coord_polar()`.
- What does `labs()` do? Read the documentation.
- What does the plot below tell you about the relationship between `city` and highway `mpg`? Why is `coord_fixed()` important? What does `geom_abline()` do?