Feature request: pal_size, pal_alpha, & pal_linewidth

[davidhodge931]

Hi,

In the same way that pal_hue, pal_shape and pal_linewidth are useful helpers, could we also have pal_size, pal_alpha and pal_linewidth functions?

Maybe this would be good for tidy developer day?

Thanks!

[teunbrand]

I think these are all pal_rescale(). Colours, shapes and linetype have constraints on their output (e.g. must be valid col, pch and lty parameters). Size, alpha and linewidth all work with numerical values, so these have no such restraints and can all be fed through the pal_rescale() function. There is a pal_area() for the size though.

[davidhodge931]

Thanks @teunbrand The use-case is mainly for something is reversed and you want to also reverse the other aesthetic to keep the order looking 'normal'. I can't work out how to use the pal_rescale() function to do this

library(tidyverse)
library(palmerpenguins)

p <- penguins |> 
  mutate(island = fct_rev(island)) |> 
  ggplot() +
  geom_point(aes(x = flipper_length_mm, 
                 y = island, 
                 size = island,
                 colour = island)) +
  scale_colour_manual(values = scales::pal_hue()(3)) +
  guides(colour = guide_legend(reverse = TRUE)) +
  guides(size = guide_legend(reverse = TRUE))

#I would like to be able to do this...
# p + 
#   scale_size_manual(values = scales::pal_size()(3))   

# I can't work out how to use scales::pal_rescale 
# p + 
#   scale_size_manual(values = scales::pal_rescale(range = c(1, 6))(3)) 

[teunbrand]

Right, so it seems this is more about the difference between discrete and continuous palettes then?

[davidhodge931]

I suppose I want to easily be able to recreate the default values for when things are reversed

[davidhodge931]

Might not work so well with the discrete/continuous thing

Maybe I'll just close.. feel free to reopen if you want to do something with this