r - ggplot2 change axis limits for each individual facet panel

Question

library(tidyverse)
ggplot(mpg, aes(displ, cty)) + 
  geom_point() + 
  facet_grid(rows = vars(drv), scales = "free")

The ggplot code above consists of three panels 4, f, and r. I'd like the y-axis limits to be the following for each panel:

Panel y-min y-max breaks
----- ----- ----- ------
4     5     25    5
f     0     40    10
r     10    20    2

How do I modify my code to accomplish this? Not sure if scale_y_continuous makes more sense or coord_cartesian, or some combination of the two.

Answer 1

This is a long-standing feature request (see, e.g., 2009, 2011, 2016) which is tackled by a separate package facetscales.

devtools::install_github("zeehio/facetscales")
library(g)
library(facetscales)
scales_y <- list(
  `4` = scale_y_continuous(limits = c(5, 25), breaks = seq(5, 25, 5)),
  `f` = scale_y_continuous(limits = c(0, 40), breaks = seq(0, 40, 10)),
  `r` = scale_y_continuous(limits = c(10, 20), breaks = seq(10, 20, 2))
)
ggplot(mpg, aes(displ, cty)) + 
  geom_point() + 
  facet_grid_sc(rows = vars(drv), scales = list(y = scales_y))

If the parameters for each facet are stored in a dataframe facet_params, we can compute on the language to create scale_y:

library(tidyverse)
facet_params <- read_table("drv y_min y_max breaks
4     5     25    5
f     0     40    10
r     10    20    2")

scales_y <- facet_params %>% 
  str_glue_data(
    "`{drv}` = scale_y_continuous(limits = c({y_min}, {y_max}), ", 
                "breaks = seq({y_min}, {y_max}, {breaks}))") %>%
  str_flatten(", ") %>% 
  str_c("list(", ., ")") %>% 
  parse(text = .) %>% 
  eval()