Feature request: could colouring of date, datetime and time variables be supported more completely?

[davidhodge931]

At present, there are only scale_colour_date and scale_colour_datetime functions available for modifying date, datetime and time colours. These appear to be equivalent to scale_colour_gradient.

This means that it is not possible to create colour steps with date, datetime or time variables.

Not is it possible to use the methods and colours/values arguments of the scale_colour_gradientn function.

It would be awesome if date, datetime and time colouring were supported more completely in this way!

[teunbrand]

For the continuous colour palettes, you can get pretty far with trans = "date" or trans = "time" (see examples below). Is there a particular thing that you're missing in date scales that we're unable to do with supplying the date transformation to continuous scales?

library(ggplot2)

ggplot(economics, aes(date, unemploy)) +
  geom_line(aes(colour = date)) +
  scale_colour_gradientn(
    colours = rainbow(10),
    trans = "date",
    breaks = scales::breaks_width("10 years")
  )

df <- data.frame(
  x = Sys.time() + seq(0, 2e6, length.out = 20),
  y = rnorm(20)
)

ggplot(df, aes(x, y)) +
  geom_line(aes(colour = x)) +
  scale_colour_viridis_c(
    trans = "time",
    breaks = scales::breaks_width("5 days")
  )

^{Created on 2022-12-09 by the reprex package (v2.0.1)}

The binned version of scales have separate issues, because binning arithmetic is currently incompatible with dates.

[davidhodge931]

Thanks @teunbrand. I was not aware that you could do this. Yes, that would allow you to do most things other than apply another trans to the date or time colour variable

[teunbrand]

Due to #5103 having been merged, I think there are now a sufficient amount of options to use date/time variables in non-position scales. Therefore, I'll thank you for this suggestion and hope you have enough tools to make this work.