add "seed" argument to request specific seed

[erikor]

If I call set.seed() prior to using geom_text_repel, I get the same layout every time as I would expect.

However, if I am using grid.arrange() (from package gridExtras) to render multiple ggplots that include geom_text_repel, then if I change the parameters (such as nudge and force) in one plot, it may result in a different layout for the other plot(s). I assume this is because rendering the first plot may take a different number of iterations depending on the settings, resulting in the RNG starting in a different place when it is time to render the next plot.

For example, if I do this:
grid.arrange(p1, p2, ncol = 2)

Then changing the parameters in p1 changes the layout in p2.

This is a problem because sometimes I want a particular seed value because it produces a "better" (as subjectively determined by the beholder) layout.

This would be avoided if I could specify the seed value to geom_text_repel directly as an argument.

[erikor]

In fact, I can make the change myself if this something you are amenable to and you add me as a contributor to the project.

[slowkow]

Thanks for opening this issue and describing the problem! I would be very happy to review a pull request with this feature.

[slowkow]

@erikor Sorry for the long delay on this issue. I fixed it in commit 0b0a7ab

I wrote some code to go through the scenario you described:

library(ggrepel)
library(gridExtra)

dat1 <- mtcars[seq(1, nrow(mtcars), 4),]
set.seed(42)
p1 <- ggplot(dat1) +
  geom_point(aes(wt, mpg), color = 'grey', size = 4, shape = 16) +
  geom_text_repel(
    aes(
      wt, mpg,
      color = factor(cyl),
      label = rownames(dat1),
      angle = -10
    ),
    size = 5
  ) +
  scale_color_discrete(name = 'cyl') +
  theme_classic(base_size = 16)

dat2 <- mtcars[seq(2, nrow(mtcars), 4),]
set.seed(42)
p2 <- ggplot(dat2) +
  geom_point(aes(wt, mpg), color = 'grey', size = 4, shape = 15) +
  geom_label_repel(
    aes(
      wt, mpg,
      color = factor(cyl),
      label = rownames(dat2)
    ),
    size = 5
  ) +
  scale_color_discrete(name = 'cyl') +
  theme_classic(base_size = 16)

grid.arrange(p1, p2, ncol = 2)

Now let's drop the "Pontiac Firebird" point and plot again:

set.seed(42)
dat3 <- dat1[rownames(dat1) != "Pontiac Firebird",]
p1 <- ggplot(dat3) +
  geom_point(aes(wt, mpg), color = 'grey', size = 4, shape = 16) +
  geom_text_repel(
    aes(
      wt, mpg,
      color = factor(cyl),
      label = rownames(dat3),
      angle = -10
    ),
    size = 5
  ) +
  scale_color_discrete(name = 'cyl') +
  theme_classic(base_size = 16)

grid.arrange(p1, p2, ncol = 2)

The plots are identical, except for the missing "Pontiac Firebird".

[erikor]

Great! Thank you.