r - ggplot2: have common facet bar in outer facet panel in 3-way plot

Question

I have the following code:

label_rev <- function(labels, multi_line = TRUE, sep = ": ") {
     label_both(rev(labels), multi_line = multi_line, sep = sep)
  }
require(ggplot2)
p <- ggplot(data = mtcars, aes(wt, mpg)) + geom_point()
p + facet_grid(vs + cyl ~ gear, labeller = label_rev)

I get the following figure:

Here is my dilemma: I would like the outerstrip of vs:0 to be only one panel encompassing the three facets (cyl:4, 6, 8) and the outstrip of vs:1 to be one panel encompassing the three facets (cyl:4, 6, 8).

Is it possible to do this using ggplot2?

Thanks again in advance for any help!

Answer 1

This can now easily be done with facet_nested() from the ggh4x package

library(ggplot2)
library(ggh4x)
p <- ggplot(data = mtcars, aes(wt, mpg)) + geom_point()
p + 
  facet_nested(vs + cyl ~ am + gear, labeller = label_both) +
  theme(panel.spacing = unit(0,"line")) 

^{Created on 2020-03-25 by the reprex package (v0.3.0)}