Get all the legends on the top of the plot - r

Question

I have a multiple plot within a plot, generated by ggpubr::ggarrange(). However the legends only appears for the first plot i.e., A and B. I wanted to get the legends for rest of the colours, C, D, E on the top. Setting common.legend = TRUE only gives the first two legends.
Thanks for the help!
library(ggpubr)
arranged_plot <- ggarrange(
plot_list[[1]] + rremove("ylab") + rremove("xlab") + rremove("x.text"),
plot_list[[2]] + rremove("ylab") + rremove("xlab") + rremove("axis.text"),
plot_list[[3]] + rremove("ylab") + rremove("xlab"),
plot_list[[4]] + rremove("ylab") + rremove("xlab") + rremove("y.text"),
labels = NULL, ncol = 2, nrow = 2,align = "hv",
font.label = list(size = 10, color = "black", face = "bold", family = NULL, position = "top"),
common.legend=TRUE)

Answer 1

I'm not sure how to do this with ggarrange, but if you're willing to look at other methods, here are two options:
Using patchwork (and collecting legends).
# sample data where each elem has cyl=4 and another cyl
mtcars$cyl <- factor(mtcars$cyl)
mtdat1 <- lapply(c(6, 8), function(CY) {
subset(mtcars, cyl %in% c(4, CY)) |>
transform(CY = CY)
})
plot_list <- lapply(mtdat1, function(dat) {
ggplot(dat, aes(mpg, disp, color = cyl)) +
geom_point() +
scale_color_manual(values = setNames(c("gray", "red", "blue"), c(4, 6, 8)), drop = FALSE)
})
library(patchwork)
plot_list[[1]] + plot_list[[2]] +
plot_layout(nrow = 1, guides = "collect") &
theme(legend.position = "top")
Facets.
# sample data, starting with `mtdat1` from above
mtdat2 <- do.call(rbind, args = mtdat1)
ggplot(mtdat2, aes(mpg, disp, color = cyl)) +
facet_wrap(~ CY) +
geom_point() +
scale_color_manual(values = setNames(c("gray", "red", "blue"), c(4, 6, 8)), drop = FALSE) +
theme(legend.position = "top")
If you prefer to not have the facet strips, we can remove those in a theme:
ggplot(mtdat2, aes(mpg, disp, color = cyl)) +
facet_wrap(~ CY) +
geom_point() +
scale_color_manual(values = setNames(c("gray", "red", "blue"), c(4, 6, 8)), drop = FALSE) +
theme(legend.position = "top", strip.text.x = element_blank())
I think there are two advantages to facets:
Simpler code, more efficient, allowing ggplot to handle everything in one step.
Since we don't explicitly free the scales (e.g., not doing scales="free"), the axes are all on the same scale, no need to explicitly control them. For comparisons as in your graph, this can be a big difference in visualizing the differences between levels. (Compare this plot with the first plot using patchwork, though those axis limits can easily be fixed as well.)