ggplot2: Divide Legend into Two Columns, Each with Its Own Title

Question

I have these factors

require(ggplot2)
names(table(diamonds$cut))
# [1] \"Fair\"      \"Good\"      \"Very Good\" \"Premium\"   \"Ideal\" 

w

Answer 1

Thank you for your example, which seemed to me to answer my problem.

However, it returns an error when I use it with a geom_sf.

Here is a reproducible example:

nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE) %>% 
  mutate(var_test=case_when(AREA<=0.05~"G1",
                            AREA<=0.10~"G2",
                            AREA>0.10~"G3"))

    ggplot(nc,aes(x=1)) +
  geom_bar(aes(fill = var_test))+ 
  scale_fill_manual(aesthetics = "fill", values = c("#ffffa8","#69159e","#f2794d"),
                    breaks =  c("G1","G2"), name = "First Group:") +
  new_scale_fill() +
  geom_bar(aes(fill2 = var_test)) %>% rename_geom_aes(new_aes = c(fill = "fill2")) +
  scale_fill_manual(aesthetics = "fill2", values = c("#ffffa8","#69159e","#f2794d"),
                    breaks = c("G3"), name = "Second Group:")

Works with geom_bar

Doesn't work with geom_sf

ggplot(nc,aes(x=1)) +
  geom_sf(aes(fill = var_test))+ 
  scale_fill_manual(aesthetics = "fill", values = c("#ffffa8","#69159e","#f2794d"),
                    breaks =  c("G1","G2"), name = "First Group:") +
  new_scale_fill() +
  geom_sf(aes(fill2 = var_test)) %>% rename_geom_aes(new_aes = c(fill = "fill2")) +
  scale_fill_manual(aesthetics = "fill2", values = c("#ffffa8","#69159e","#f2794d"),
                    breaks = c("G3"), name = "Second Group:")

Error: Can't add `o` to a ggplot object.
Run `rlang::last_error()` to see where the error occurred.

Thanks for your help.