Rau, Roland wrote:
> Dear all,
>
> let's assume I have a vector of character strings:
>
> x <- c("abcdef", "defabc", "qwerty")
>
> What I would like to find is the following: all elements where the word
> 'abc' does not appear (i.e. 3 in this case of 'x').
>
a quick shot is:
x[-grep("abc", x)]
which unfortunately fails if none of the strings in x matches the
pattern, i.e., grep returns integer(0); arguably, x[integer(0)] should
rather return all elements of x:
"An empty index selects all values" (from ?'[')
but apparently integer(0) does not count as an empty index (and neither
does NULL). so you may want something like:
strings = c("abcdef", "defabc", "qwerty")
pattern = "abc"
if (length(matching <- grep(pattern, strings))) x[-matching] else x
vQ
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