Create border and title for each column in `facet_wrap`

Question

I want to put black borders with labels and titles around each facet in facet_wrap. Something similar to this:

Sample data:

library(tidyverse)

mtcars %>% 
  mutate(gear = factor(gear, levels = c(4, 3, 5))) %>%
  ggplot(aes(mpg, disp)) + 
  geom_point() + 
  geom_smooth(method = "lm") + 
  facet_wrap(~am + gear)

maybe helpful https://stackoverflow.com/questions/28652284/how-to-change-color-of-facet-borders-when-using-facet-grid and https://stackoverflow.com/questions/46220242/ggplot2-outside-panel-border-when-using-facet/46236791 — tjebo, Dec 01 '19 at 14:49
just to clarify - you want the border not around each facet, but around each column of ? — tjebo, Dec 01 '19 at 14:49
Thank you for the links, I'm looking into them. Yes, I wouldn't like around each facet per-se but around each column in this case. — DJV, Dec 01 '19 at 14:51
I actually wouldn't really mind if it will be just around the columns, as I can arrange the facets order to match what ever order I want. — DJV, Dec 01 '19 at 14:53
I think what you want to achieve is not easy without some hacking. I wonder if you may not want to overthink the aesthetic of your plot - maybe simply draw borders around the entire plot? You could plot your facets in several distinct plots and easily add a border and title [like in this question](https://stackoverflow.com/questions/52175766/draw-border-around-certain-rows-using-cowplot-and-ggplot2) — tjebo, Dec 01 '19 at 18:17
@Tjebo I was thinking about it as my "plan B". I was hoping maybe someone will have a better/easier solution :) — DJV, Dec 01 '19 at 21:46
I'm not sure that I understood the question, but under `facet_wrap()`. Next I just want to border each column — DJV, Dec 04 '19 at 21:13
With pleasure - I learned from it too :) I guess one could consider accepting the answer? There seems to be not much activity here otherwise.. — tjebo, Dec 06 '19 at 15:06

score 2 · Accepted Answer · edited Dec 04 '19 at 07:40

You can do this by manually adding to the ggplot gtable:

library(tidyverse)    
library(grid)
library(gtable)

p <- mtcars %>% 
  mutate(gear = factor(gear, levels = c(4, 3, 5))) %>%
  ggplot(aes(mpg, disp)) + 
  geom_point() + 
  geom_smooth(method = "lm") + 
  facet_wrap(~am + gear)

g <- ggplotGrob(p)

# add basic black rectangle round the columns
gt <- gtable_add_grob(g, 
                     gList(
                      rectGrob(gp = gpar(col = "black", lwd=3, fill=NA)), 
                      rectGrob(gp = gpar(col = "black", lwd=3, fill=NA))),
                     t=7, b=13, l=c(5, 9))
# look
# grid.newpage(); grid.draw(gt)

# add title above columns
tit1 <-  textGrob("title1", x=0, hjust=0) ; tit2 =  textGrob("title2", x=0, hjust=0) 
gt <- gtable_add_rows(gt, grobHeight(tit1) + unit(0.5, "line"), 0)
gt <- gtable_add_grob(gt, gList(tit1, tit2), t=1, l=c(5, 9))
# draw
grid.newpage(); grid.draw(gt)

thanks @Tjebo; I picked up wee bit from [Baptiste's](https://stackoverflow.com/users/471093/baptiste) answers, and he provides a quick guide [here](https://cran.r-project.org/web/packages/gridExtra/vignettes/gtable.html) — user20650, Dec 04 '19 at 10:48
There may be another way now with this cool new package : https://www.stat.auckland.ac.nz/~paul/Reports/gggrid/gggrid.html — user20650, Oct 14 '21 at 23:49

Create border and title for each column in `facet_wrap`

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