How to rotate y axis title (not label) to be horizontal in ggplot2

Question

How to rotate y axis title (not label) to be horizontal in ggplot2? Many thanks for help!

a1 %>% ggplot(aes(x=c(1:8), y=ev)) +
  geom_bar(stat="identity", width=0.3, color="black", fill="grey") +
  ylab("%")

user_12993861 · Answer

This could be achieved via theme(axis.title.y = element_text(angle = 0, vjust = 0.5))

library(ggplot2)

ggplot(mtcars, aes(hp, mpg)) +
  geom_point() +
  theme(axis.title.y = element_text(angle = 0, vjust = 0.5))