grep with special characters

Question

I want to find the elements that contains star character in the following vector.

s <- c(\"A\",\"B\",\"C*\",\"D\",\"E*\")
grep(\"*\",s)

[1] 1 2 3 4 5


        

Answer 1

You need to escape special characters twice, once for R and once for the regular expression:

grep('\\*', s)

Answer 2

You may want to see this link, see https://r.789695.n4.nabble.com/Why-do-my-regular-expressions-require-a-double-escape-to-get-a-literal-td4437962.html. As Berend Hasselman mentioned:

you need the \\ because the expression between tour quotes is interpreted twice.

Answer 3

Another option is to use fixed=TRUE

grep('*', s,fixed=TRUE)