Backreferencing in R (Regular Expressions)

Question

I'm not sure why I can't get a simple back reference to work in R/RStudio.

grepl('name\1','namename') returns FALSE. grepl('(name)\1','namename') is no good either. What am I doing wrong?

Thanks!

Answer 1

Use the double backlash before 1 (the regex engine will understand it as a single backslash):

grepl('(name)\\1', 'namename')
## [1] TRUE

This is because:

cat('(name)\\1')
## (name)\1

In your case, \1 == \001 means an ASCII character of code 1.

charToRaw('\1')
## [1] 01