regex -> negate a word

Gabor Grothendieck wrote:

Try this:


# values
setdiff(x, grep("abc", x, value = TRUE))

Another possibility is:

z <- "abc"
x0 <- c(x, z) # to handle no match case
x0[- grep(z, x0)] # values

on quick testing, these two and the if-based version have comparable
runtime, with a minor win for the last one, and if the input is moderate
this makes no real difference.

however, the second solution above is likely to fail if the pattern is
more complex, e.g., contains a character class or a wildcard:

strings = c("xyz")
pattern = "a[a-z]"
strings[-grep(pattern, c(strings, pattern))]
# character(0)


vQ