Remove "group" legend in ggplot

Question

So a handful of posts already address how to remove unwanted legends in ggplot.

The wonderful answer posted to "Remove extra legends in ggplot2" suggests:

For any mapped variable you can supress the appearance of a legend by using guide = 'none' in the appropriate scale_...

However, I'm having problems with unwanted legends being created by adding the group aesthetic. I tried the scale approach, but it doesn't seem to work with the group argument:

could not find function "scale_group"

A search here didn't provide any insight on the proper function call to modify group aesthetics either.

User @joran provided the following insight in the linked post above:

That's because the group aesthetic doesn't generate any scales or guides on its own. It's always sort of modifying something else. You'll never get a legend for the group aesthetic.

Example

So I could just add show.legend = FALSE to my function call containing group to remove any legend for that function, but this doesn't work out if I want some other portion (i.e., aesthetic) of that call to be included in the legend.

#Set Up Example:

library(lme4)
library(ggplot2)

mod <- lmer(mpg ~ hp + (1 |cyl), data = mtcars)
pred <- predict(mod,re.form = NA)
pdat <- data.frame(mtcars[,c('hp','cyl')], mpg = pred, up = pred+1, low = pred-1)

Adding show.legend = F to function calls work as expected:

gp <- 
  ggplot(data = mtcars, aes(x = hp, y = mpg, color = cyl, group = cyl), show.legend = F) +
  geom_point(aes(group = cyl),show.legend = F) +
  facet_wrap(~cyl) + 
  geom_line(data = pdat, aes(group = cyl),show.legend = F, color = 'orange')

But when I want to add a legend for a geom_ribbon fill based on the same group (and therefore cannot use the show.legend = F argument), I get a legend for my group again...

gp + geom_ribbon(data = pdat, aes(ymin = low, ymax = up, group = cyl, fill = 'mod'), alpha = 0.3) + 
scale_fill_manual(values=c("orange"), name="model")

The outputs:

It's because it's inheriting the color aesthetic (you can see it in the outline of the ribbons). If you only set that in geom_point, it will go away. — alistaire
@alistaire ohhhhh. So by assigning color in the main ggplot function call, all subsequent function calls are "activating" (not sure the right word to use) the color call (and thus creating a legend for it unless supressed using show.legend=F)? Is that right? — theforestecologist
@theforestecologist: what's your expected output? only model legend without cyl gradient scale? — Tung
Use inherit.aes = FALSE such as geom_ribbon(data = pdat, aes(x = hp, ymin = low, ymax = up, group = cyl, fill = 'mod'), inherit.aes = FALSE, alpha = 0.3) — Tung
@theforestecologist Yep, provided that geom plots the aesthetic in some way (here the outline of the ribbon). If you look in a geom's docs (?geom_ribbon here), it will tell you which aesthetics it understands. — alistaire

CCwudi CCwudi · Accepted Answer · 2021-01-12T02:40:53

The last geom cover the first geom, you can try this

ggplot(data = mtcars, aes(x = hp, y = mpg, color = cyl, group = cyl), show.legend = F) +
  geom_point(aes(group = cyl)) +                             
  facet_wrap(~cyl) + 
  geom_line(data = pdat, aes(group = cyl),color = 'orange') 

gp + geom_ribbon(data = pdat, aes(ymin = low, ymax = up, group = cyl, fill = 'mod'),       alpha = 0.3) + 
  scale_fill_manual(values=c("orange"), name="model")+
  scale_color_continuous(guide ='none')

By the way, my idea comes from the link you posted at the top.

Remove "group" legend in ggplot

1 Answers