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rregexstringsymbols

Extract position of "+" and "*" symbol in string using R

I am looking for a manner to extract the position of "*" and "+" symbols in R string.

test <- "x+y"
unlist(gregexpr("+", test))
[1] 1 2 3
unlist(gregexpr("y", test))
[1] 3

It returns the position of x or y but returns all positions for + or *.

Thank you!

Solution

  • Use fixed = TRUE, by default it is FALSE and uses the regex mode where + is a metacharacter. According to ?regex

    + - The preceding item will be matched one or more times.

    * - The preceding item will be matched zero or more times.

    unlist(gregexpr("+", test, fixed = TRUE))
[1] 2