drop = FALSE does not work in scale_*_manual

[cpauvert]

Hi,
Thank you very much for this package! However, I was puzzled to see that the option drop = FALSE was not passed along when provided through ... in scale_color_manual for instance.

library(igraph)
gr <- make_graph('bull')
#Adding a categorical value
V(gr)$Cat<-c("A","A","A","B","B")
library(ggraph) # v1.0.2     and ggplot2 v3.0.0
layout <- create_layout(gr, layout = 'igraph', algorithm = 'kk')
ggraph(layout)+geom_node_point(aes(color=Cat))+geom_edge_link()+
  coord_fixed()+theme_void()+
  # Trying to map all possible values
  scale_color_manual(values = c("A"="red","B"="blue","C"="black"),drop=FALSE)

Only the red and blue nodes are shown in the plot, which is expected. But the legend should mention the "C" category and the black label.

Do you have any ideas?
Best,
Charlie

[malcolmbarrett]

This is just because Cat only has levels "A" and "B". The same behavior occurs in ggplot.

df <- data.frame(x = 1:3, y  = 1:3, z = factor(c("A", "B", "B")))

ggplot(df, aes(x, y, col = z)) + 
  geom_point() +
  scale_color_manual(values = c("A" = "red", "B" = "blue", "C" = "black"), drop=FALSE)

So you just need to tell it the levels.

layout$Cat <- factor(layout$Cat, levels = c("A", "B", "C"))

ggraph(layout) +
  geom_node_point(aes(color = Cat)) + 
  geom_edge_link() +
  coord_fixed()+
  theme_void()+
  scale_color_manual(values = c("A" = "red", "B" = "blue", "C" = "black"), drop = FALSE)

[cpauvert]

Hi!
Thank you very much @malcombarrett ! I overlooked factors indeed.
Best,
Charlie

[Artur-man]

I think this doesnt work anymore because the same script above is giving empty point in the legend

[goesjon]

Same problem here but haven't found a solution yet. If anyone has a solution, please let me know.

[sporella]

Its a change included in ggplot2 version 3.5.0 more info here

Following the example here, you need to add show.legend = T

 ggraph(layout) +
  geom_node_point(aes(color = Cat), show.legend = T) + 
  geom_edge_link() +
  coord_fixed()+
  theme_void()+
  scale_color_manual(values = c("A" = "red", "B" = "blue", "C" = "black"), drop = FALSE)