scales::rescale* functions cannot use \(x) x notation

[davidhodge931]

I assume this is an error with scales::rescale* functions and not ggplot2.

library(tidyverse)

#this works using ~ .x notation
ggplot(mpg, aes(displ, hwy, colour = cty - mean(cty))) +
  geom_point() +
  labs(
    x = "Engine displacement [L]",
    y = "Highway miles per gallon",
    colour = "Centered\nvalue"
  ) +
  scale_colour_stepsn(
    colours = c("blue", "white", "red"), 
    rescaler = ~scales::rescale_mid(.x, mid = 0), 
    breaks = scales::breaks_width(5),
  )

#this doesn't work using \(x) notation
ggplot(mpg, aes(displ, hwy, colour = cty - mean(cty))) +
  geom_point() +
  labs(
    x = "Engine displacement [L]",
    y = "Highway miles per gallon",
    colour = "Centered\nvalue"
  ) +
  scale_colour_stepsn(
    colours = c("blue", "white", "red"), 
    rescaler = \(x) scales::rescale_mid(x, mid = 0), 
    breaks = scales::breaks_width(5),
  )
#> Error in rescaler(...): unused argument (from = c(-7.85897435897436, 18.1410256410256))

^{Created on 2023-06-18 with reprex v2.0.2}

[davidhodge931]

  library(tidyverse)
#this also doesn't work using function(x) notation
ggplot(mpg, aes(displ, hwy, colour = cty - mean(cty))) +
  geom_point() +
  labs(
    x = "Engine displacement [L]",
    y = "Highway miles per gallon",
    colour = "Centered\nvalue"
  ) +
  scale_colour_stepsn(
    colours = c("blue", "white", "red"), 
    rescaler = function(x) scales::rescale_mid(x, mid = 0), 
    breaks = scales::breaks_width(5),
  )
#> Error in rescaler(...): unused argument (from = c(-7.85897435897436, 18.1410256410256))

^{Created on 2023-06-18 with reprex v2.0.2}

[teunbrand]

The reason \(x) and function(x) anonymous functions don't work, is because there are multiple arguments passed to the rescaler function: the values and the limits (iirc).

[hadley]

Yeah, this is nothing to do with anonymous function syntax and everything to do with expected arguments.