CODEWITHSUNDEEP
rregex
Seth Brundle
Seth Brundle

Reputation: 170

Regex issue in R when escaping regex special characters with str_extract

I'm trying to extract the status -- in this case the word "Active" from this pattern:

Status\nActive\nHometown\

Using this regex: https://regex101.com/r/xegX00/1, but I cannot get it to work in R using str_extract. It does seem weird to have dual escapes, but I've tried every possible combination here and cannot get this to work. Any help appreciated!

mutate(status=str_extract(df, "(?<=Status\\\\n)(.*?)(?=\\\\)"))

Upvotes: 2

Views: 133

Answers (2)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626926

Your regex fails because you tested it against a wrong text.

"Status\nActive\nHometown" is a string literal that denotes (defines, represents) the following plain text:

Status
Active
Hometown

In regular expression testers, you need to test against plain text!

To match a newline, you can use "\n" (i.e. a line feed char, an LF char), or "\\n", a regex escape that also matches a line feed char.

You can use

library(stringr)
x <- "Status\nActive\nHometown\n"
stringr::str_extract(x, "(?<=Status\\n).*") ## => [1] "Active"
## or
stringr::str_extract(x, "(?<=Status\n).*")  ## => [1] "Active"

See the R demo online and a correct regex test.

Note you do not need an \n at the end of the pattern, as in an ICU regex flavor (used in R stringr regex methods), the . pattern matches any chars other than line break chars, so it is OK to just use .* to match the whole line.

Upvotes: 0

Ronak Shah
Ronak Shah

Reputation: 389047

You can use sub in base R -

x <- "Status\nActive\nHometown\n"
sub('.*Status\n(.*?)\n.*', '\\1', x)
#[1] "Active"

If you want to use stringr, here is a suggestion with str_match which avoids using lookahead regex

stringr::str_match(x, 'Status\n(.*)\n')[, 2]
#[1] "Active"

Upvotes: 3

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