gghighlight creating extra points

Question

gghighlight seems to be creating extra points when I highlight. Any tips here? I imagine I must be doing something wrong.

library(tidyverse)
library(gghighlight)
mtcars<-mtcars

#produces as expected
ggplot(mtcars) + 
  geom_jitter(aes(x=factor(cyl),y=wt,col=factor(gear)),show.legend = FALSE)
#produces as expected

#creates extra points?
ggplot(mtcars) + 
  geom_jitter(aes(x=factor(cyl),y=wt,col=factor(gear)),show.legend = FALSE)+gghighlight::gghighlight(wt>3,label_key = gear)

Edit, adding plots:

Answer 1

Does indeed seem to be the case:

library(tidyverse)
library(gghighlight)

mtcars <- mtcars

#using geom_point insted of geom_jitter since geom_jitter adds noise to the points, thus making plots tougher to reproduce and compare:

#no highlight:
ggplot()+
  geom_point(mtcars, mapping = aes(x = factor(cyl),y = wt,col = factor(gear)), show.legend = FALSE,, position=position_dodge(width = 0.5))

#with highlight:
ggplot()+
  geom_point(mtcars, mapping = aes(x = factor(cyl),y = wt,col = factor(gear)), show.legend = FALSE, position=position_dodge(width = 0.5))+
  gghighlight(wt > 3,label_key = gear)

see grey points for cyl=6 to the left of the red points labelled with a "3".

#new points seem to appear for cyl=6 (grey ones to the left), so lets look at these specifically:
#first: how many values should be there?
only_cyl_6 <- subset(mtcars, mtcars$cyl==6)
length(only_cyl_6$wt)
#7 
#but we see 6 points in our first plot. A quick look @ only_cyl_6 reveals that #two values have the same wt value:
only_cyl_6
# -> Merc 280 & Merc 280C      
#so the first plot seems to be fine...geom_jitter supports this.

ggplot()+
  geom_jitter(only_cyl_6, mapping = aes(x = factor(cyl),y = wt,col = factor(gear)), show.legend = FALSE)

#now we see 7 point. thats good.

#lets add highlight again:

ggplot()+
  geom_jitter(only_cyl_6, mapping = aes(x = factor(cyl),y = wt,col = factor(gear)), show.legend = FALSE)+
  gghighlight(wt > 3,label_key = gear)

Now there are 9. So in conclusion: adding highlight does indeed seem to make additional points being plotted...