Legend mis-alignement for parsing greek letters using scale::parse_format

[Sibojang9]

In the first figure, the right-hand side legend is correctly aligned with the regular ggplot code. However, the greek characters were mis-aligned when labels=parse_format() is used to parse "microgram" in the second figure, as indicated by the gap (white space) next to the legend "1 ug". The erratic alignment behavior sounds like a bug to me.

library(ggplot2)
library(scales)
data <- data.frame(x=c(1,2),y=c(1,2),c= c("10000~mu*g","1~mu*g"))
ggplot(data,aes(x=x,y=y,color=c)) + geom_point()

ggplot(data,aes(x=x,y=y,color=c)) + geom_point()+ scale_colour_discrete(labels=parse_format()) 

^{Created on 2022-04-25 by the reprex package (v2.0.1)}

[thomasp85]

While poorly documented, the default justification for expressions in labels has always been right-aligned. This can of course be overwritten in the guide. I can't comment on the reason for this decision as it predates my time with ggplot2 (meaning it is ancient 🙂). This also means that it is probably too late to change as others may likely rely on the default behaviour...

[Sibojang9]

This is a typical sunk cost fallacy. It will take more toll to fix in future.

[thomasp85]

Well, it's not really a bug so there is nothing to fix later. It was a poorly documented behaviour that is now properly documented.

[Sibojang9]

Do you have the link to the docu?

[thomasp85]

ggplot2/R/guide-legend.r

Lines 34 to 36 in eb0010e

	#' @param label.hjust A numeric specifying horizontal justification of the
	#' label text. The default for standard text is 0 (left-aligned) and 1
	#' (right-aligned) for expressions.

[Sibojang9]

Thank you so much for sharing.