ggplot: remove NA factor level in legend

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How can I omit the NA level of a factor from a legend?

Pesky NA legend value.....

From the nycflights13 database, I created a new continuous variable called tot_delay, and then created a factor called delay_class with 4 levels. When I plot, I filter out NA values, but they still appear in the legend. Here's my code:

library(nycflights13); library(ggplot2)

flights$tot_delay = flights$dep_delay + flights$arr_delay
flights$delay_class <- cut(flights$tot_delay,                                   
                           c(min(flights$tot_delay, na.rm = TRUE), 0, 20 , 120,
                             max(flights$tot_delay, na.rm = TRUE)),   
                           labels = c("none", "short","medium","long"))     

filter(flights, !is.na(tot_delay)) %>% 
  ggplot() +
  geom_bar(mapping = aes(x = carrier, fill = delay_class), position = "fill")
ggplot2 r
3 Answers

The parent example isn't a good illustration of the problem (of course unexpected NA values should be tracked down and eliminated), but this is the top result on Google so it should be noted that there is a now an option in scale_XXX_XXX to prevent NA levels from displaying in the legend by setting na.translate = F. For example:

# default    
ggplot(data = data.frame(x = c(1,2,NA), y = c(1,1,NA), a = c("A","B",NA)),
           aes(x, y, colour = a)) + geom_point(size = 4)

enter image description here

# with na.translate = F    
ggplot(data = data.frame(x = c(1,2,NA), y = c(1,1,NA), a = c("A","B",NA)),
           aes(x, y, colour = a)) + geom_point(size = 4) + 
           scale_colour_discrete(na.translate = F)

enter image description here

This works in ggplot2 3.1.0.

user_34715160
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