How to italicize one category in a legend in ggplot2

Question

For my legend in ggplot2 I have 2 categories, how do I italicize only 1 category and not the other?

As an example, consider the following plot. How can I set "Manual" in italics?

library(ggplot2)

ggplot(data = mtcars, aes(x = as.factor(am), fill = as.factor(am))) + 
  geom_bar() + 
  scale_fill_discrete(
    "Transmission",
    breaks = c(0, 1),
    labels = c("Automatic", "Manual")
  )

^{Created on 2020-01-01 by the reprex package (v0.3.0)}

Answer 1

You can use expression and italic to create italicized text on labels.

library(ggplot2)

ggplot(data = mtcars, aes(x = as.factor(am), fill = as.factor(am))) + 
  geom_bar() + 
  scale_fill_discrete(
    "Transmission",
    breaks = c(0, 1),
    labels = c("Automatic", expression(italic("Manual")))
  )

^{Created on 2020-01-01 by the reprex package (v0.3.0)}