scale_{colour,fill}_manual(limits = ...) doesn't limit the scale

[yutannihilation]

(I found this during looking at the examples on scale_manual.)

It seems scale_{colour,fill}_manual(limits = ...) doesn't limit the scale actually (but limit the legend).

library(ggplot2)
library(patchwork)

p <- ggplot(mtcars, aes(factor(cyl))) +
  geom_bar(aes(fill = factor(cyl)))

# this drops 6
p1 <- p + scale_fill_discrete(limits = c("4", "8"))

# this doesn't
cols <- c("8" = "red", "4" = "blue", "6" = "darkgreen", "10" = "orange")
p2 <- p + scale_fill_manual(values = cols, limits = c("4", "8"))

p1 / p2

^{Created on 2019-04-24 by the reprex package (v0.2.1)}

[thomasp85]

Do you think we can fix this for 3.2.0?

[yutannihilation]

I forgot to reply here. After a quick look, I think there are two possible fixes:

1. Add limits argument to manual_scale() and subset values before creating a palette from the values.
2. Raise an error when limits is provided.

First one seems straightforward, but I enumerate the second because manual_scale() can accept pal while it's difficult to limit the pal and it might be confusing.

If we go with the first, probably it will be something like this:

manual_scale <- function(aesthetic, values = NULL, ..., limits = NULL) {
  ...
  if (!is.null(limits)) {
    values <- values[values %in% limits]
  }

  pal <- function(n) {
  ...