Extract part of string between two different patterns

regex r text-extraction stringr
Marta Karas picture Marta Karas · Apr 8, 2014 · Viewed 7.2k times · Source

I try to use stringr package to extract part of a string, which is between two particular patterns.

For example, I have: 

my.string <- "nanaqwertybaba"
left.border  <- "nana"
right.border <- "baba"

and by the use of str_extract(string, pattern) function (where pattern is defined by a POSIX regular expression) I would like to receive:

"qwerty"

Solutions from Google did not work.

Answer

Henrik picture Henrik · Apr 8, 2014

In base R you can use gsub. The parentheses in the pattern create numbered capturing groups. Here we select the second group in the replacement, i.e. the group between the borders. The . matches any character. The * means that there is zero or more of the preceeding element 

gsub(pattern = "(.*nana)(.*)(baba.*)",
     replacement = "\\2",
     x = "xxxnanaRisnicebabayyy")
# "Risnice"

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