Rotate switched facet labels in ggplot2 facet_grid

Solution 1:

You just need to add the theme() and specify the angle in strip.text.y.left.

library(tidyverse)
library(reshape2)

df <- group_by(mpg, manufacturer) %>%
  summarise(cty = mean(cty), hwy = mean(hwy)) %>%
  ungroup()

df <- melt(df, id.vars = "manufacturer")

ggplot() +
  geom_bar(data =df, aes(x = variable, y = value), stat = "identity") +
  facet_grid(manufacturer ~ ., switch = "y")+
  theme(strip.text.y.left = element_text(angle = 0))

^{Created on 2020-03-15 by the reprex package (v0.3.0)}

Note that strip.text.y.left was added in ggplot2 3.3.0. For earlier versions, you need to write strip.text.y = element_text(angle = 180).