r - Character "|" in strsplit function (vertical bar / pipe)

Question

I was curious about:

> strsplit("ty,rr", split = ",")  
[[1]]
[1] "ty" "rr"

> strsplit("ty|rr", split = "|")
[[1]]
[1] "t" "y" "|" "r" "r"

Why don't I get c("ty","rr") from strsplit("ty|rr", split="|")?

Answer 1

It's because the split argument is interpreted as a regular expression, and | is a special character in a regex.

To get round this, you have two options:

Option 1: Escape the |, i.e. split = "\|"

strsplit("ty|rr", split = "\|")
[[1]]
[1] "ty" "rr"

Option 2: Specify fixed = TRUE:

strsplit("ty|rr", split = "|", fixed = TRUE)
[[1]]
[1] "ty" "rr"

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Please also note the See Also section of ?strsplit, which tells you to read ?"regular expression" for details of the pattern specification.