How to perl regex match in R in the grepl function?

Question

I have a function in R which uses the grepl command as follows:

function(x) grepl('\bx\b',res$label, perl=T)

This doesn't seem to work - the 'x' input is a character type string (a sentence), and i'd like to create word boundaries around the 'x' as I match, as I don't want the term to pull out other terms in the table I am searching through which contains some similar terms.

Any suggestions?

Answer 1

You just need to properly escape the slash in your regex

ff<-function(x) grepl('\\bx\\b',x, perl=T)
ff(c("axa","a x a", "xa", "ax","x"))
# [1] FALSE  TRUE FALSE FALSE  TRUE

Answer 2

如果您只是想知道字符串是否是句子而不是单个单词，则可以使用： function(x) grepl('\\\\s',x)