I'm having trouble understanding the syntax of meta-characters used in R regex functions. For example, I have the following character vector;
x<-c("See 053 2001",
"Related to 0324 2015")
If I use the grep function to match the string of numbers separated by a space character and my basic understanding of regular expressions, I'd write the following (i.e., should work):
grep("F[0-9]{4}\s[0-9]", x, value = TRUE)
#returning 'Error: '\s' is an unrecognized escape in character string
#starting ""F[0-9]{4}\s"'
Okay, that's confusing to me, given that the Regular Expressions as used in R Documentation states
Symbols \d, \s, \D and \S denote the digit and space classes and their negations...
However, from playing around and reading other [regex] questions on stack overflow, I note the following does find the match I'm looking for.
grep("F[0-9]{4}\\s[0-9]", x)#Or
grep("F[0-9]{4} [0-9]", x)
[1] 2
I'd guess this has to do with the way a character string is processed in R, with it's own escape characters. Can someone elaborate here?
