Override horizontal positioning with ggrepel

Question

I\'m working on a chart similar to a slopegraph, where I\'d like to put labels along one or both sides with ample blank space to fit them on both sides. In cases where label

Answer 1

TL;DR: probably a bug

Long answer:

I think it might be a bug in the code. I checked the gtable of the plot you made, wherein the hjust was specified numerically and correctly:

# Assume 'g' is the plot saved under the variable 'g'
gt <- ggplotGrob(g)
# Your number at the end of the geom may vary
textgrob <- gt$grobs[[6]]$children$geom_text_repel.textrepeltree.1578
head(textgrob$data$hjust)

[1] 1 0 1 0 1 0

Which got me thinking that (1) the plot can't be fixed by messing around in the gtable and (2) the drawtime code for the textrepeltree class of grobs may contain some errors. This makes sense, since the labels are repositioned when the plot device is resized. So when we look at the makeContent.textrepeltree() code in the link you provided, we can see that the hjust parameter is passed on to makeTextRepelGrobs(). Let's have a look at the relevant formals:

makeTextRepelGrobs <- function(
  ...other_arguments...,
  just = "center",
  ...other_arguments...,
  hjust = 0.5,
  vjust = 0.5
) { ...body...}

We can see that hjust is a valid argument, but there also exists a just argument, which is an argument that is not passed on from makeContent.textrepeltree().

When we look at the function body there are these two lines:

  hj <- resolveHJust(just, NULL)
  vj <- resolveVJust(just, NULL)

Where resolveH/VJust are imported from the grid package. The resolveHJust() essentially checks whether the second argument is NULL and if that is true, default to the first argument, otherwise return the second argument. You can see that the hjust that was passed on to makeTextRepelGrobs() does not get passed to resolveHJust(), and this seems to be the point where your hjust parameter is dropped unexpectedly.

Further down the code is where the actual text grobs are made:

  t <- textGrob(
    ...other_arguments...
    just = c(hj, vj),
    ...other_arguments...
  )

I imagine that the fix would be relatively straightforward: you would just have to supply hjust as the second argument to resolveHJust(). However, since that makeTextRepelGrobs() is internal to ggrepel and does not get exported, you would have to copy a lot of extra code to get this to work. (Not sure if only copying the makeTextRepelGrob() would be sufficient, haven't tested this)

All of this leaves me to conclude that the hjust that you specified in geom_text_repel() gets lost at the last moment of drawtime by the makeTextRepelGrobs() internal function.

Answer 2

UPDATE (12 December 2019):

FYI, this is now addressed in the development version of ggrepel, and the fix also applies to geom_label_repel. See issue #137 on GitHub.

library(ggplot2)
library(dplyr)
devtools::install_github("slowkow/ggrepel")


df <- structure(list(long_lbl = c("chevrolet, k1500 tahoe 4wd, auto(l4)", 
                                  "chevrolet, k1500 tahoe 4wd, auto(l4)", "subaru, forester awd, manual(m5)", 
                                  "subaru, forester awd, manual(m5)", "toyota, camry, manual(m5)", 
                                  "toyota, camry, manual(m5)", "toyota, toyota tacoma 4wd, manual(m5)", 
                                  "toyota, toyota tacoma 4wd, manual(m5)", "volkswagen, jetta, manual(m5)", 
                                  "volkswagen, jetta, manual(m5)"), year = c(1999L, 2008L, 1999L, 
                                                                             2008L, 1999L, 2008L, 1999L, 2008L, 1999L, 2008L), mean_cty = c(11, 
                                                                                                                                            14, 18, 20, 21, 21, 15, 17, 33, 21)), class = c("tbl_df", "tbl", 
                                                                                                                                                                                            "data.frame"), row.names = c(NA, -10L))

df_wrap <- df %>%  
  mutate(wrap_lbl = stringr::str_wrap(long_lbl, width = 25))

# With geom_text_repel
ggplot(df_wrap, aes(x = year, y = mean_cty, group = long_lbl)) +
  geom_line() +
  geom_text_repel(aes(label = wrap_lbl),
                  hjust = "outward",
                  direction = "y",
                  seed = 57,
                  min.segment.length = 100) +
  scale_x_continuous(expand = expansion(add = 10))

# With geom_label_repel
ggplot(df_wrap, aes(x = year, y = mean_cty, group = long_lbl)) +
  geom_line() +
  geom_label_repel(aes(label = wrap_lbl),
                  hjust = "outward",
                  direction = "y",
                  seed = 57,
                  min.segment.length = 100) +
  scale_x_continuous(expand = expansion(add = 10))