How to remove empty panel in 2-way facet_grid?

Question

I want to remove the whole panel from ggplot 2-way facet_grid. I have taken some lead from this question. Here is the code with example data

library(ggplot2)
library(ggh4x)

df <- data.frame(x=rnorm(80),y=rnorm(80),
                  col=rep(c(" ", "B","C"," ","B","C","B","C"),each=10),
                  row=rep(c("a","a","a","b","b","b","c","c"),each=10))

ggplot(data=df,aes(x=x,y=y))+
  geom_point()+
  facet_grid2(row~col, scales = "free", independent = "all")

I want to remove the left panel. How can it be done?

Answer 1

Noted from your comment that subsetting the dataset beforehand isn't an option for you, so here's a post-production approach:

# create plot
p <- ggplot(data=df,aes(x=x,y=y))+
  geom_point()+
  facet_grid2(row~col, scales = "free", independent = "all")

# convert to grob
gp <- ggplotGrob(p)

# check which are the columns of the gtable to strip out
# (for the example, we want to strip out content from cols 4-5)
gp                             # examine layout in console
gtable::gtable_show_layout(gp) # examine layout in viewer

# strip them out
gp <- gp %>%
  cowplot::gtable_remove_grobs(names = gp$layout %>% 
                                 filter(r %in% 4:5) %>% 
                                 pull(name)) %>%
  cowplot::gtable_squash_cols(cols = 4:5)

# plot the result
plot(gp)

data:

set.seed(123)
df <- data.frame(x=rnorm(80),y=rnorm(80),
                 col=rep(c(" ", "B","C"," ","B","C","B","C"),each=10),
                 row=rep(c("a","a","a","b","b","b","c","c"),each=10))