r - How to strsplit using '|' character, it behaves unexpectedly?

Question

I would like to split a string of character at pattern "|"

but

unlist(strsplit("I am | very smart", " | "))

[1] "I"     "am"    "|"     "very"  "smart"

or

gsub(pattern="|", replacement="*", x="I am | very smart")    

[1] "*I* *a*m* *|* *v*e*r*y* *s*m*a*r*t*"

Answer 1

| is a metacharacter. You need to escape it (using \ before it).

> unlist(strsplit("I am | very smart", " \| "))
[1] "I am"       "very smart"
> sub(pattern="\|", replacement="*", x="I am | very smart")
[1] "I am * very smart"

Edit: The reason you need two backslashes is that the single backslash prefix is reserved for special symbols such as (newline) and (tab). For more information look in the help page ?regex. The other metacharacters are . | ( ) [ { ^ $ * + ?