CODEWITHSUNDEEP
regexrstringtext-extraction
Cam B
Cam B

Reputation: 195

Extracting Number and Name from String [r]

POSIX Expression is giving me a headache.

Lets say we have a string:

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

and ultimately I would like to be able to have:

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

I've had a look at the stringr package but cant figure out how to extract the information out using regular expressions and str_split.

Any help would be greatly appreciated.

Cameron

Upvotes: 3

Views: 2366

Answers (4)

Kay
Kay

Reputation: 2854

expanding on flodel's answer - this would be the most concise solution, i think:

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

Upvotes: 0

Hansi
Hansi

Reputation: 2644

I'd do it this way:

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

Upvotes: 0

Tommy
Tommy

Reputation: 40821

This should work in you 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"

An alternative for extracting everything in parentheses from the first part:

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

Upvotes: 3

flodel
flodel

Reputation: 89067

So if I understand correctly you want to extract the elements within parenthesis.

You can first extract those elements, including the parenthesis, using str_extract_all:

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

Since str_extract_all returns a list, let's turn it into a vector:

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

Last, you can remove the parenthesis (the first and last character of each string) using str_sub:

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

Edit: A few comments about the regex pattern: \\( and \\) are your opening and closing parenthesis. .*? means any character string but without being greedy, otherwise you would get one long match from the first ( to the last ).

Upvotes: 3

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