In R: grab all alnum characters before the first punctuation

Question

I have a vector s of strings (or NAs), and would like to get a vector of same length of everything before first occurrence of punctionation (.).

Answer 1

You can remove all symbols (incl. a newline) from the first dot with the following Perl-like regex:

s <- c("ABC1.2", "22A.2", NA)
gsub("[.][\\s\\S]*$", "", s, perl=T)
## => [1] "ABC1" "22A"  NA  

See IDEONE demo

The regex matches

• [.] - a literal dot
• [\\s\\S]* - any symbols incl. a newline
• $ - end of string.

All matched strings are removed from the input with "". As the regex engine analyzes the string from left to right, the first dot is matched with \\., and the greedy * quantifier with [\\s\\S] will match all up to the end of string.

If there are no newlines, a simpler regex will do: [.].*$:

gsub("[.].*$", "", s)

See another demo