Extract number and name from string [r]

POSIX Expression is giving me a headache.

Let's say we have a line:

a = "[question(37), question_pipe(\"Person10\")]"


and ultimately I would like to be able to:

b = c("37", "Person10")


I have looked at the package stringr

but cannot figure out how to extract information from regex and str_split


Any help would be greatly appreciated.



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4 answers

So, if I understood correctly, you want to extract the items in parentheses.

You can extract these elements first, including the parentheses, using str_extract_all


b1 <- str_extract_all(string = a, pattern = "\\(.*?\\)")
# [[1]]
# [1] "(37)"           "(\"Person10\")"


Since it str_extract_all

returns a list, include it in the vector:

b2 <- unlist(b1)
# [1] "(37)"           "(\"Person10\")"


Finally, you can remove the parenthesis (first and last character of each line) with str_sub


b3 <- str_sub(string = b2, start = 2L, end = -2L) 
# [1] "37"           "\"Person10\""


Edit: a few comments about the regex pattern: \\(

and \\)

are the opening and closing brackets. .*?

means any string of characters, but no greedy one, otherwise you will get one long match from first (

to last )




This should work in your specific case:

a <- "[question(37), question_pipe(\"Person10\")]"

# First split into two parts
b <- strsplit(a, ",")[[1]]

# Extract the number (skip as.integer if you want it as character)
x <- as.integer(gsub("[^0-9]","", b[[1]])) # 37

# Extract the stuff in quotes
y <- gsub(".*\"(.*)\".*", "\\1", b[[2]])   # "Person10"


Alternative for extracting everything in brackets from the first part:

x <- gsub(".*\\((.*)\\).*", "\\1", b[[1]]) # "37"




I would do it like this:

a <- "[question(37), question_pipe(\"Person10\")]"
b <- unlist(strsplit(gsub("\"","",gsub(".*question\\((.*)\\).*question_pipe\\((.*)\\).*","\\1,\\2",a)),","))
[1] "37"       "Person10"




expanding on the flop answer - this would be the shortest solution I think:

a <- "[question(37), question_pipe(\"Person10\")]"    
b1 <- unlist(str_extract_all(string = a, pattern = "\(.*?\)"))
b <- gsub("[[:punct:]]", "", b1)




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