strip.text.y = element_blank() yields an error when there are multiple layers of strip labels

[yqgchen]

Hello,
I was trying to remove the strip labels. I found that setting strip.text.x = element_blank() works when there is only one layer of strip labels and yields an error when there are multiple layers of labels. Is there any way to remove the strip labels in the latter case? Many thanks!

# This works:
p1 <- ggplot(mtcars, aes(x = mpg, y = wt)) + geom_point() +
 facet_grid(vs + am ~ gear)  + theme(strip.text.x = element_blank())

#This does not work:
p2 <- ggplot(mtcars, aes(x = mpg, y = wt)) + geom_point() +
 facet_grid(vs + am ~ gear)  + theme(strip.text.y = element_blank())
#Error in gtable_add_grob(panel_table, strips$y$right, panel_pos_rows$t,  : 
#  Not all inputs have either length 1 or same length same as 'grobs'

[yutannihilation]

Thanks, confirmed. The error comes from here:

ggplot2/R/facet-grid-.r

Line 407 in 01df437

panel_table <- gtable_add_grob(panel_table, strips$y$right, panel_pos_rows$t, -2, clip = "on", name = paste0("strip-r-", seq_along(strips$y$right)), z = 2)

  # Check that inputs have the right length
  if (!all(vapply(
    list(t, r, b, l, z, clip, name), len_same_or_1,
    logical(1), n_grobs
  ))) {
    stop("Not all inputs have either length 1 or same length same as 'grobs'")
  }

https://github.com/r-lib/gtable/blob/4fb86c724c0555de9ce3fce867e2320fe9aeb9c2/R/add-grob.r#L57-L63

I have no idea what's happening here, sorry...

[teunbrand]

I have an idea where this problem comes form. If the strips texts are rendered as blanks, you get strangely formatted grobs for the strips with incorrect lengths.

library(ggplot2)

# Create full theme and theme with blank strip.text.y.right
theme_full <- theme_gray()
theme_blank <- theme_full + theme(strip.text.y.right = element_blank())

# Dummy labels
dummy <- data.frame(c("a", "b"), "b")

# Render strips
strip_full  <- ggplot2:::render_strips(dummy, dummy, label_value, theme_full)
strip_blank <- ggplot2:::render_strips(dummy, dummy, label_value, theme_blank)

# The normal strips are a list of tablegrobs
strip_full$y$right
#> [[1]]
#> TableGrob (1 x 2) "strip": 2 grobs
#>   z     cells  name                  grob
#> 1 1 (1-1,1-1) strip gTree[strip.gTree.83]
#> 2 2 (1-1,2-2) strip gTree[strip.gTree.87]
#> 
#> [[2]]
#> TableGrob (1 x 2) "strip": 2 grobs
#>   z     cells  name                  grob
#> 1 1 (1-1,1-1) strip gTree[strip.gTree.85]
#> 2 2 (1-1,2-2) strip gTree[strip.gTree.89]

# The 'blank' themed strips are a matrix of lists?
strip_blank$y$right
#>      [,1]   [,2]  
#> [1,] List,3 List,3
#> [2,] List,3 List,3

# They have different lengths
length(strip_full$y$right)
#> [1] 2
length(strip_blank$y$right)
#> [1] 4

When you then naively try to add the blank strips to a gtable and not all arguments are length 1 you can get the error described. Below I use t = c(1, 2) because the surrounding code would assume render_strips() returns a length two list.

library(gtable)

gt <- gtable(unit(c(1, 1), "cm"), unit(c(1, 1), "cm"))

# Works fine
new_full <- gtable_add_grob(gt, strip_full$y$right, t = c(1, 2), l = 1)

# Returns the error
new_blank <- gtable_add_grob(gt, strip_blank$y$right, t=  c(1, 2), l = 1)
#> Error in gtable_add_grob(gt, strip_blank$y$right, t = c(1, 2), l = 1): Not all inputs have either length 1 or same length same as 'grobs'

^{Created on 2020-06-09 by the reprex package (v0.3.0)}

I hope this could help narrow the scope of the problem a bit.

[yutannihilation]

Thanks for your insight!