R how to change one of the level to NA

Question

I have a data set and one of its column has factor levels \"a\" \"b\" \"c\" \"NotPerformed\". How can I change all the \"NotPerformed\" factors to

Answer 1

I revise my old answer and provide what you can do as of September 2016. With the development of the dplyr package, now you can use recode_factor() to do the job.

x <- factor(c("a", "b", "c", "NotPerformed"))

# [1] a            b            c            NotPerformed
# Levels: a b c NotPerformed

library(dplyr)
recode_factor(x, NotPerformed = NA_character_)
# [1] a    b    c    
# Levels: a b c