count the number of occurrences of "(" in a string

r stringr
NPHARD picture NPHARD · Feb 22, 2017 · Viewed 14.7k times · Source

I am trying to get the number of open brackets in a character string in R. I am using the str_count function from the stringr package

s<- "(hi),(bye),(hi)"
str_count(s,"(")

Error in stri_count_regex(string, pattern, opts_regex = attr(pattern, : ` Incorrectly nested parentheses in regexp pattern. (U_REGEX_MISMATCHED_PAREN)

I am hoping to get 3 for this example

Answer

sebastian-c picture sebastian-c · Feb 22, 2017

( is a special character. You need to escape it:

str_count(s,"\\(")
# [1] 3

Alternatively, given that you're using stringr, you can use the coll function:

str_count(s,coll("("))
# [1] 3

Related questions

Splitting a dataframe string column into multiple different columns

What I am trying to accomplish is splitting a column into multiple columns. I would prefer the first column to contain "F", second column "US", third "CA6" or "DL", and the fourth to be "Z13" or "U13" etc etc. My …

Read More
Extracting a string between other two strings in R

I am trying to find a simple way to extract an unknown substring (could be anything) that appear between two known substrings. For example, I have a string: a<-" anything goes here, STR1 GET_ME STR2, anything goes …

Read More
regex multiple pattern with singular replacement

I am trying to replace both "st." and "ste." with "st". Seems like the following should work but it does not: require("stringr") county <- c("st. landry", "ste. geneveve", "st. louis") str_replace_all(county, c("st\\.", "ste\\."), "…

Read More