scale_*_continuous labels = fun_name failure

[EvaMaeRey]

I like the idea of doing the following to label an axis via the axis text (instead of the axis title). I don't have a good sense of why it doesn't work in the third example however (mtcars) when the same scale_y_continuous info is included. My best guess is it is a corner case, where the max label value is not printed because it's at plot edge, and that introduces the NAs, but I'm not really not sure.

library(tidyverse)
# ggram:::clearhistory()

label_max_diamonds <- function(x){
        ifelse(x == max(x), paste0(x, '\ndiamonds'), 
          x)}

diamonds |>
  ggplot() +
  aes(x = cut) +
  geom_bar() + 
  scale_y_continuous(labels = label_max_diamonds) 

MASS::birthwt |>
  ggplot() +
  aes(x = factor(smoke)) +
  geom_bar() + 
  scale_y_continuous(labels = label_max_diamonds)

mtcars |>
  ggplot() +
  aes(x = factor(am)) +
  geom_bar()

last_plot() + 
  scale_y_continuous(labels = label_max_diamonds)

^{Created on 2025-04-24 with reprex v2.1.1}

[teunbrand]

I exchanged some words with Elio on a very similar challenge. Open the link at your own risk. You might not be able to unsee something and it'll haunt you.
https://mastodon.social/@eliocamp/113247425724915007

[teunbrand]

I think that is unrelated, but using x == max(x, na.rm = TRUE) should resolve this.

[EvaMaeRey]

I never noticed the detail of some gridlines not being labeled at the extremes of rendered plots!

[EvaMaeRey]

I just added "\n" before x to address the centering brought up with @eliocamp, in this easy case which doesn't uses scales package because I couldn't follow the wizardry of the other approach. 🤷‍♀️

[EvaMaeRey]

Wizardry:

element_text_first_line <- function(...) {
  el <- element_text(...)
  class(el) <- union("element_text_first_line", class(el))
  el
}

element_grob.element_text_first_line <- 
  function(element, label, x = NULL, y = NULL, ...) {
    twolines <- grepl("\n", label)
    y <- y - unit(twolines * 0.5, "lines")
    NextMethod()
  }

[teunbrand]

Hey extensions are extensions, even if they don't use the ggproto system ^_^