ggplot italicize part of caption AND divide text over two lines

Question

I like to add the following caption to my graph:

Note: Market concentration averages in the United States, United Kingdom, and the Netherlands are, respectively, 1920, 1388, and 1244

Where 'Note:' needs to be italicized, and 'Netherlands are, respectively, 1920, 1388, and 1244' should be placed on a new line.

Using the paste function, I can italize a part. But using the \n within paste, mixes every thing up as you can see here (this is an edited image, made using Paul's advice below):

I tried various other solutions, but without succes. Here is the code I am using:

library(ggplot2)

note = expression(paste(italic("Note: "), "Market concentration averages in the United States, United Kingdom, and the \nNetherlands are, respectively, 1920, 1388, and 1244"))

gg <- ggplot(mtcars, aes(wt, mpg)) + geom_point()+

# Title
labs(caption=note)

gg + theme(plot.caption=element_text(size=7.5, hjust=0, margin=margin(t=15)))

I'd save some frustration and grob-machinations and use `magick` to post-annotate the caption. — hrbrmstr, Nov 08 '17 at 18:23
that'd be optimal @Gregor but there are still alignment bugs in grobs with newlines and mixed formatting. `magick` annotations will be much easier in the long run. — hrbrmstr, Nov 08 '17 at 18:33
@Gregor I get what you mean. I now inlcuded a minimal and reproducible example. — Rens, Nov 08 '17 at 19:31
@hrbrmstr thanks, if all other solutions fail, I will try post-annotation — Rens, Nov 08 '17 at 19:33

score 10 · Accepted Answer · edited Apr 22 '19 at 18:26

Based on this answer,

library(grid)
library(ggplot2)


ggplot(iris, aes(Sepal.Length, Sepal.Width)) +
  geom_line() + 
  labs(caption= "First~line \n italic('and a second,')~bold('fancy one') \n
       'also,'~integral(f(x)*dx, a, b)~'for good measure'")+
  (theme_grey() %+replace% theme(plot.caption = element_custom()))

element_custom <- function() {
  structure(list(), class = c("element_custom", "element_text"))
}

element_grob.element_custom <- function(element, label="", ...)  {
  disect <- strsplit(label, "\\n")[[1]]
  labels <- lapply(disect, function(x) tryCatch(parse(text=x), 
                                                error = function(e) x))
  hl <-  unit(rep(1, length(labels)), 'strheight', data=labels) + unit(0.1,"line")
  yl <- c(list(unit(0,"line")), 
          lapply(seq_along(labels[-length(labels)]), function(ii) sum(hl[1:ii])))

  cl <- do.call(gList, Map(function(label, ii) 
    textGrob(label, y = unit(1,"npc")-yl[[ii]], hjust=0, x=0, vjust=1), 
    label = labels, ii = seq_along(labels)))

  gTree(children = cl, cl="sl", heights = hl, gp=gpar(col="grey50",fontsize=8))
}

heightDetails.sl <- function(x) sum(x$heights)

score 4 · Answer 2 · answered Nov 08 '17 at 21:07

4

Does this give you what you want ?

note = expression(paste(italic("Note: \n "), 
                        "Market concentration averages in the United States, United Kingdom, and the \nNetherlands are, respectively, 1920, 1388, and 1244"))

(The difference is that the "Note" part now also includes a newline)

answered Nov 08 '17 at 21:07

Paul Murrell

226
2
3

Dear Paul, this almost gives what I want. According to the journal guidelines the second line needs to start where the first line starts too. So 'Note' and 'Netherlands' both start at the Y-axis. I tried somethings but this also did not work out well. Any advice would be very welcome! – Rens Nov 09 '17 at 14:47

score 2 · Answer 3 · answered Jan 04 '18 at 22:32

Here is a different approach: just create empty space in the ggplot2 plot (by adding a blank caption) then navigate to the viewport that ggplot2 created for the caption and draw your caption as separate lines of text.

library(grid)

ggplot(mtcars, aes(wt, mpg)) + geom_point() + 
       labs(caption=expression(atop(" ", " ")))

grid.force()
downViewport("caption.9-4-9-4")
## grid.rect()
grid.text(expression(paste(italic("Note: "), 
                           "Market concentration averages in the United States, United Kingdom, and the")),
          x=0, y=unit(1, "npc") - unit(1, "line"), just=c("left", "top"),
          gp=gpar(fontsize=7.5))
grid.text("Netherlands are, respectively, 1920, 1388, and 1244",
          x=0, y=unit(1, "npc") - unit(2, "line"), just=c("left", "top"),
          gp=gpar(fontsize=7.5))

Hope that helps

ggplot italicize part of caption AND divide text over two lines

3 Answers3

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