y-axis labels on opposite sides in `facet_wrap`

Question

I would like to plot a facet_wrap of 2 groups, and have the y-axis labels on the left on the left plot, and the right on the right plot.

Here is the normal behavior. Both y-axis labels on the left.

library(tidyverse)

mtcars %>% mutate(let = rep(LETTERS[1:2], times = nrow(mtcars)/2),
                       make = rownames(mtcars))  %>% 
ggplot(aes(y = make, x = mpg)) + 
geom_point() +
facet_wrap(~ let, scales = "free")

^{Created on 2023-05-15 with reprex v2.0.2}

I would like to have the B plot y-axis labels on the right side of the plot, but keep the A axis labels on the left side of the plot. Is this possible?

Answer 1

One option is to make two plots and use patchwork to combine them:

library(dplyr)
library(ggplot2)
quux <- mtcars %>%
  mutate(
    let = rep(LETTERS[1:2], times = nrow(mtcars)/2),
    make = rownames(mtcars)
  )
gg1 <- filter(quux, let == "A") %>%
  ggplot(aes(y = make, x = mpg)) +
  geom_point() +
  facet_wrap(~ let, scales = "free")
gg2 <- filter(quux, let == "B") %>%
  ggplot(aes(y = make, x = mpg)) +
  geom_point() +
  facet_wrap(~ let, scales = "free") +
  scale_y_discrete(position = "right")

library(patchwork)
gg1 + gg2