Improved beeswarm layout based on ggdist talk discussion Wed

[mjskay]

@jbengler asked a good question at the {ggdist} talk on Wed: is there a nice-looking beeswarm layout algorithm that doesn't end up with visual asymmetry in small groups? I didn't have an answer at the time, but it occurred to me today that a minor modification to the "swarm" layout in {ggdist} (which uses the "compact swarm" layout from {beeswarm}) might do the trick.

Here is the normal swarm layout as I was demoing on Wed:

library(ggplot2)
library(ggdist)

set.seed(12345)
data.frame(
  x = rnorm(100, c(1,2)),
  y = c("a","b")
) |>
  ggplot(aes(x = x, y = y, fill = x > 2, group = NA)) +
  geom_dots(layout = "swarm", side = "both") +
  theme_ggdist()

Notice that in small clusters it can be visually asymmetrical. If we re-center contiguous clusters on their mean y position, most of the asymmetry disappears (code same as above, using a ggdist branch):

If you open the images in two separate tabs and flip back and forth you can see what's happening more easily. This is a simple change that I think results in a strictly better layout. It also breaks up the continuous center line of the swarms a bit, which IMO is good --- I've never been a big fan of that visual artifact. I will likely (after some additional testing) just replace the "swarm" layout in {ggdist} with this.

[jbengler]

Hi @mjskay,

Wow, this is fantastic—thanks so much for taking it on!
It’s tackling a long-standing discomfort I’ve had with swarm plots in R ;)

Best,
Broder

[mjskay]

My pleasure! :)

[electrolars]

Wow, that's fantastic. Thank you for taking on this problem.

[jbengler]

Hey @mjskay,

I still really love your solution to the swarm asymmetry problem. While trying out the most recent ggdist version, I noticed that it doesn’t seem to have made it into the released version yet—am I right?

Did you run into any issues with the implementation, or is it more a matter of time and priorities? I’d absolutely love to be able to use your solution in my plots someday.

Best,
Broder