Combining new lines and italics in facet labels with ggplot2

Question

I have a problem getting some words used in facet labels in italics. I use the following code to create new lines for the labels:

    levels(length_subject$CONSTRUCTION) <- 
c("THAT \n Extraposed", "THAT \n Post-predicate", "TO \n Extraposed \n for-subject", "TO \n Post-predicate \n for-subject", "THAT \n Extraposed \n that-omission", "THAT \n Post-predicate \n that-omission")

However, I want the words "that" and "for" to appear in italics. I've tried something like

"TO \n Extraposed \n (italics(for))-subject"

bit it doesn't work.

This is what the plots look like:

enter image description here

produced with the following code:

ggplot( length_subject, aes( x = SUBJECT ) ) +
  geom_histogram(binwidth=.6, colour="black", fill="grey") +
  ylab("Frequency") +  
  xlab("Subject length") +  
  scale_x_discrete(breaks=c(2,4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30)) + #
  facet_grid( SUBJECT_TYPE~CONSTRUCTION, scales="free_x", space="free") +
  theme(strip.text.x = element_text(size = 8))

Here is a reduced variant of the data:

structure(list(ID = structure(1:86, .Label = c("A05_122_01", 
"A05_253_01", "A05_277_07", "A05_400_01", "A05_99_01", "A06_1076_01", 
"A06_1261_01", "A06_1283_01", "A06_1283_02", "A06_1317_01", "A06_1326_01", 
"A06_1389_01", "A06_1390_01", "A06_1437_01", "A06_1441_02", "A06_1441_03", 
"A06_1442_03", "A06_1456_01", "A06_1461_01", "A06_830_01", "A06_868_01", 
"A06_884_01", "A06_884_03", "A0K_1057_02", "A0K_1144_07", "A0K_1177_01", 
"A0K_1190_03", "A0K_1214_03", "A0K_1216_01", "A0K_950_02", "A0K_986_01", 
"A1A_102_02", "A1A_163_01", "A1A_199_01", "A1A_45_01", "A1A_97_01", 
"A1B_1008_02", "A1B_1013_01", "A1B_1028_02", "A1B_1042_01", "A1B_1064_01", 
"A1B_1126_03", "A1B_1152_01", "A1B_1174_01", "A1B_1271_01", "A1B_997_01", 
"A1J_487_01", "A1J_544_02", "A1J_555_03", "A1J_569_01", "A1J_601_01", 
"A1N_422_04", "A1N_70_02", "A1S_191_01", "A1S_329_01", "A1S_330_01", 
"A1S_465_04", "A1Y_248_01", "A1Y_278_02", "A1Y_292_01", "A1Y_466_01", 
"A1Y_521_01", "A1Y_612_01", "A1Y_634_01", "A26_139_03", "A26_142_01", 
"A26_148_01", "A26_289_01", "A26_345_02", "A26_439_01", "A26_441_02", 
"A26_463_01", "A28_171_01", "A28_244_01", "A28_245_01", "A28_30_01", 
"A28_341_01", "A28_42_01", "A28_494_03", "A2A_301_01", "A2A_396_01", 
"A2A_599_01", "A2A_637_01", "A2A_676_01", "A2E_22_01", "A2E_25_03"
), class = "factor"), SUBJECT = c(3L, 2L, 6L, 2L, 2L, 1L, 1L, 
1L, 1L, 2L, 4L, 1L, 4L, 2L, 3L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 7L, 1L, 3L, 2L, 2L, 1L, 6L, 7L, 4L, 1L, 5L, 4L, 2L, 9L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 3L, 5L, 3L, 4L, 1L, 1L, 1L, 1L, 5L, 
2L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 5L, 2L, 1L, 2L, 2L, 1L, 7L, 1L, 
4L, 1L, 2L, 1L, 1L, 3L, 1L, 13L, 2L, 1L, 1L, 1L, 3L, 1L, 1L), 
    CONSTRUCTION = structure(c(1L, 3L, 1L, 1L, 1L, 4L, 4L, 1L, 
    1L, 5L, 5L, 1L, 1L, 5L, 1L, 3L, 5L, 1L, 5L, 4L, 3L, 3L, 1L, 
    5L, 3L, 5L, 1L, 1L, 2L, 3L, 1L, 1L, 3L, 1L, 1L, 1L, 3L, 1L, 
    4L, 3L, 1L, 3L, 1L, 1L, 1L, 1L, 4L, 2L, 4L, 1L, 1L, 3L, 2L, 
    5L, 1L, 1L, 1L, 3L, 1L, 1L, 4L, 4L, 3L, 1L, 2L, 3L, 3L, 1L, 
    3L, 1L, 1L, 1L, 6L, 1L, 1L, 2L, 4L, 4L, 3L, 5L, 3L, 3L, 3L, 
    3L, 5L, 1L), .Label = c("THAT_EXT", "THAT_EXT_NT", "THAT_POST", 
    "THAT_POST_NT", "TO_EXT_FOR", "TO_POST_FOR"), class = "factor"), 
    SUBJECT_TYPE = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 
    2L, 1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 2L, 2L, 2L, 2L, 
    1L, 1L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 3L, 1L, 1L, 
    2L, 3L, 1L, 2L, 2L, 3L, 1L, 3L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 
    1L, 1L, 1L, 2L, 2L, 3L, 2L, 2L, 2L, 3L, 1L, 1L, 2L, 1L, 1L, 
    2L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 
    1L, 3L, 3L), .Label = c("NP", "PRO", "PROPER"), class = "factor")), .Names = c("ID", 
"SUBJECT", "CONSTRUCTION", "SUBJECT_TYPE"), class = "data.frame", row.names = c(NA, 
-86L))

A thought: try `labeller = label_parsed` inside `facet_grid`. Not sure what that will do to your new lines though. — joran, May 10 '13 at 20:35
@joran I the get the following error message: Error in parse(text = x) : :3:5: unexpected '-' 2: Extraposed 3: for- ^ — user1504579, May 10 '13 at 20:57
@joran I will update the post to include a reproducible example. — user1504579, May 10 '13 at 20:58
you can't really mix `expression()` and newlines in R; the usual workaround is to use `atop`. — baptiste, May 10 '13 at 21:09

score 11 · Accepted Answer · answered May 10 '13 at 21:10

To get italics, you need the formatting described in plotmath (and then for that to be parsed as an expression). However, the plotmath syntax does not have a line break operation. You can get something similar with atop, though. With your given example, you can set the labels to

levels(length_subject$CONSTRUCTION) <- 
  c("atop(textstyle('THAT'),textstyle('Extraposed'))", 
    "atop(textstyle('THAT'),textstyle('Post-predicate'))",
    "atop(atop(textstyle('TO'),textstyle('Extraposed')),italic('for')*textstyle('-subject'))",
    "atop(atop(textstyle('TO'),textstyle('Post-predicate')),italic('for')*textstyle('-subject'))",
    "atop(atop(textstyle('THAT'),textstyle('Extraposed')),italic('that')*textstyle('-omission'))",
    "atop(atop(textstyle('THAT'),textstyle('Post-predicate')),italic('that')*textstyle('-omission'))")

and then adding labeller=label_parsed to the facet_grid call

ggplot( length_subject, aes( x = SUBJECT ) ) +
  geom_histogram(binwidth=.6, colour="black", fill="grey") +
  ylab("Frequency") +  
  xlab("Subject length") +  
  scale_x_discrete(breaks=c(2,4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30)) + #
  facet_grid( SUBJECT_TYPE~CONSTRUCTION, scales="free_x", space="free", 
              labeller=label_parsed) +
  theme(strip.text.x = element_text(size = 8))

gives

enter image description here

It's not perfect (the spacing between lines is not the same, and the disparity would only get worse the more lines there are), but that is the only way I've found to combine the two (newlines in plotmath expressions).

Thank you. It would be nice to find a way to fix the spacing though. — user1504579, May 10 '13 at 21:19

baptiste · Answer 2 · 2016-03-25T02:05:21.767

Edit (2016)

With the new facet labelling system, this solution does not work anymore. The trick of inheriting from element_blank to make a custom grob is now explicitly disabled. I guess the lesson is to accept that some things cannot be done in ggplot2, by design, and not waste too much energy with workarounds that may get broken at any time in the future.

Original answer

You could try to create a suitable custom element to place in the theme settings. The theme design does not make it very easy, unfortunately,

require(ggplot2)
require(gridExtra) # tableGrob

element_grob.element_custom <- function(element, label="", ...)  {

  mytheme <- ttheme_minimal(core = list(fg_params = list(parse=TRUE)))
  disect <- strsplit(label, "\\n")[[1]]

  g1 <- tableGrob(as.matrix(disect), theme=mytheme)
  # wrapping into a gTree only because grobHeight.gtable would be too tight
  # cf. absolute.units() squashing textGrobs
  gTree(children=gList(g1), height=sum(g1$heights), 
        cl = "custom_strip")
}

# gTrees don't know their size and ggplot would squash it, so give it room
grobHeight.custom_strip = heightDetails.custom_axis = function(x, ...)
  x$height
# silly wrapper to fool ggplot2's inheritance check...
facet_custom <- function(...){
  structure(
    list(...), # this ... information is not used, btw
    class = c("element_custom","element_blank", "element") # inheritance test workaround
  ) 

}


title <- c("First~line \n italic('wait, a second')", 
           "this~is~boring",
           "integral(f(x)*dx, a, b)")

iris2 <- iris
iris2$Species <- factor(iris$Species, labels=title)
ggplot(iris2, aes(Sepal.Length, Sepal.Width)) +
  geom_line() + facet_grid(.~Species) +
  theme(strip.text.x = facet_custom())

score 0 · Answer 3 · answered Feb 20 '18 at 19:37

0

As several of you were looking for how to fix the spacing, I have found a solution. Add a line with atop(scriptscriptstyle("") before the last line from 3 lines (making this 4) or any following lines and don't forget to add ) afterwards

answered Feb 20 '18 at 19:37

O. Bertrand

71
3

Combining new lines and italics in facet labels with ggplot2

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