Using regex in R to detect a specific word anywhere in string

Question

I'm trying to write regular expressions in R to detect a word that can occur anywhere within a string, but only when it occurs as an entire word. e.g. in

samplestr <- c("LT BLAHBLAH", "BLAH LT BLAH", "BLAHLT BLOO")

I want to detect all occurances of "LT" but not cases where a word contains LT within a larger group. Desired output of grepl("regex that works",samplestr) (or similar string detection function) would be:

TRUE TRUE FALSE

This seems to be an exact duplicate of [this](https://stackoverflow.com/questions/66631361/regex-in-r-to-detect-exact-word) — Mata, Nov 04 '21 at 09:17

score 0 · Accepted Answer · answered Nov 04 '21 at 09:13

You may use grep with the regex pattern \bLT\b:

samplestr <- c("LT BLAHBLAH", "BLAH LT BLAH", "BLAHLT BLOO")
output <- grep("\\bLT\\b", samplestr, value=TRUE)
output

[1] "LT BLAHBLAH"  "BLAH LT BLAH"

The pattern \bLT\b has word boundaries on either side of LT, which will only match LT when as a standalone word, or, more generally, when surrounded by non word characters.

Using regex in R to detect a specific word anywhere in string

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