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How to replace matches in a string and index each match

A particular string can contain multiple instances of a pattern that I'm trying to match. For example, if my pattern is <N(.+?)N> and my string is "My name is <N Timon N> and his name is <N Pumba N>", then there are two matches. I want to replace each match with a replacement that includes an index for which match is being replaced.

So in my string "My name is <N Timon N> and his name is <N Pumba N>", I want to change the string to read "My name is [Name #1] and his name is [Name #2]".

How do I accomplish this, preferably with a single function? And preferably using functions from stringr or stringi?

Solution

  • You can do this with gregexpr and regmatches in Base R:

    my_string = "My name is <N Timon N> and his name is <N Pumba N>"

# Get the positions of the matches in the string
m = gregexpr("<N(.+?)N>", my_string, perl = TRUE)

# Index each match and replace text using the indices
match_indices = 1:length(unlist(m))

regmatches(my_string, m) = list(paste0("[Name #", match_indices, "]"))

    Result:

    > my_string
# [1] "My name is [Name #1] and his name is [Name #2]"

    Note:

    This solution treats the same match as a different "Name" if it appears more than once. For example the following:

    my_string = "My name is <N Timon N> and his name is <N Pumba N>, <N Timon N> again"


m = gregexpr("<N(.+?)N>", my_string, perl = TRUE)

match_indices = 1:length(unlist(m))

regmatches(my_string, m) = list(paste0("[Name #", match_indices, "]"))

    outputs:

    > my_string
[1] "My name is [Name #1] and his name is [Name #2], [Name #3] again"