Manual fill scale guide issue with unused factor level

[jmgirard]

I found a problem with the guide for a manual fill scale when a factor level is unused.

I expected the guide tile for group C to be green instead of transparent/grey.

Here is the code to reproduce the bug:

library(ggplot2)

data <- data.frame(
  x = c(1, 2, 3, 4),
  ymin = c(1, 1, 2, 2),
  ymax = c(2, 2, 3, 3),
  group = factor(c("A", "B", "A", "B"), levels = c("A", "B", "C"))
)

ggplot(data, aes(x = x, ymin = ymin, ymax = ymax, fill = group)) +
  geom_ribbon() +
  scale_fill_manual(
    values = c("A" = "red", "B" = "blue", "C" = "green"),
    limits = c("A", "B", "C"),
    drop = FALSE
  )

^{Created on 2024-11-25 with reprex v2.1.1}

[teunbrand]

Hi there, thanks for the report! Since ggplot2 3.5.0 we require data to be present to show the key in the legend or to set geom_*(show.legend = TRUE) if it should be shown regardless. This issue has been reported before in #5728.

[jmgirard]

library(tidyverse)

data <- data.frame(
  x = c(1, 2, 3, 4),
  ymin = c(1, 1, 2, 2),
  ymax = c(2, 2, 3, 3),
  group = factor(c("A", "B", "A", "B"), levels = c("A", "B", "C"))
)

ggplot(data, aes(x = x, ymin = ymin, ymax = ymax, fill = group)) +
  geom_ribbon(show.legend = TRUE) +
  scale_fill_manual(
    values = c("A" = "red", "B" = "blue", "C" = "green"),
    limits = c("A", "B", "C"),
    drop = FALSE
  )

^{Created on 2024-11-25 with reprex v2.1.1}