Unexpected regex behavior when executed in base R

Question

As per this link, I wrote a regex that does not give the expected result when executed for a specific string in R:

string <- "0,9% BB"
regex  <- "^ ?\\d+[\\d ,\\.]*[B-DF-HJ-NP-TV-Z\\/]*%?"   
grep(regex, string, value = T, perl = T)

The result output is

 [1] "0,9% BB"

instead of the desired (and outputed by the link)

[1] "0,9%"

What am I missing to get the desired output? Preferably base R, please.

score 1 · Answer 1 · answered Apr 17 '21 at 15:37

1

This returns "0,9%" using only base R

string <- "0,9% BB"
regex  <- "^ ?\\d+[\\d ,\\.]*[B-DF-HJ-NP-TV-Z\\/]*%?"
regmatches(x = string, m = regexpr(regex,string,perl = TRUE))

answered Apr 17 '21 at 15:37

John Girardot

Great, thank you. However, I really can´t figure out why it does not work when using grep () ... – Fabio Correa Apr 17 '21 at 16:26
I’m thinking grep() on its own returns the whole string if a match is found. – John Girardot Apr 17 '21 at 16:36
1

Sure! grep("a", "abc", value = T, perl = T) results "abc". Thanks again. – Fabio Correa Apr 17 '21 at 16:56

1 Answers1