Use ggplot2 and units package to define aesthetic mappings

Question

I would like to create a plot where a variable (say z) defines a colour scheme for some points in a ggplot. For example:

library(ggplot2)
library(units)
#> udunits database from C:/Users/user/AppData/Local/R/win-library/4.3/units/share/udunits/udunits2.xml
set.seed(1)
dat <- data.frame(
 x = 1:5, 
 y = 1:5, 
 z = runif(5)
)
ggplot(dat) + 
 geom_point(aes(x, y, col = z))

However, as soon as I specify that the variable z is recorded with a given unit of measurement, the same code fails

dat$z <- set_units(dat$z, "m")
ggplot(dat) + 
 geom_point(aes(x, y, col = z))
#> Error in Ops.units(x, range[1]): both operands of the expression should be "units" objects

^{Created on 2024年05月23日 with reprex v2.0.2}

Is it possible to fix the previous code?

• Gregor Thomas: color = as.numeric(z)?
• agila: Yes, sure but, IMO, that kinda defeats the point of using the units package. Maybe this is just currently not implemented, and I can create a feature request at GitHub page of the units package.
• Gregor Thomas: And the NEWS file suggests that this has been part of the units package since version 0.8.0, and this resolved issues shows use of units::scale_x_units.
• Gregor Thomas: Hmm, yes it does seem they made a strange choice to implement scale_x_units and scale_y_units, but ignore the other scales. I would suggest opening an issue in the units package.
• agila: Just for reference, I opened a new issue here.