CODEWITHSUNDEEP
rstringlisttype-conversion
steves
steves

Reputation: 331

Given a list as string, how to convert back to list of numbers?

I am given a string which was a list of numbers:

s <- "[14,7,5,3,4,0,1,7,2,3,1,18,13,4,23,7,8,8,11,18,15,6,2,10,2,4,8,5,11,5,1,5,2,4,3,1,6,8,5,5,3,1,1,4,5,2,9,3,4,11,11,14,3,12,2,6,0,0,15,1,18,5,3,6,6,6]"

Please guide me how to convert it back to regular list of numbers? I have tried using strsplit, as.data.frame but it seems very long. I want something efficient and creative.

Upvotes: 3

Views: 159

Answers (3)

Rana Usman
Rana Usman

Reputation: 1051

Here's the R base solution

This line will only extract digits and save it into a list.

numbers <- regmatches(s, gregexpr("[[:digit:]]+", s))

Unlisting the list and converting it into numeric.

numbers <- as.numeric(unlist(numbers))

Result

 [1] 14  7  5  3  4  0  1  7  2  3  1 18 13  4 23  7  8  8 11 18 15  6  2 10  2  4  8  5 11  5  1  5  2  4
[35]  3  1  6  8  5  5  3  1  1  4  5  2  9  3  4 11 11 14  3 12  2  6  0  0 15  1 18  5  3  6  6  6

Upvotes: 1

G. Grothendieck
G. Grothendieck

Reputation: 269396

1) JSON The input shown in the question is in JSON format so use either the jsonlite or rjson package and it will do the needed string processing for you.

library(jsonlite)
fromJSON(s)

giving:

 [1] 14  7  5  3  4  0  1  7  2  3  1 18 13  4 23  7  8  8 11 18 15  6  2 10  2
[26]  4  8  5 11  5  1  5  2  4  3  1  6  8  5  5  3  1  1  4  5  2  9  3  4 11
[51] 11 14  3 12  2  6  0  0 15  1 18  5  3  6  6  6

2) strapply If you did want to use string processing anyways then one option would be strapply extracting all sequences of digits "\\d+" and converting to numeric giving the same output as above.

library(gsubfn)
strapply(s, "\\d+", as.numeric, simplify = c)

3) scan or without any packages or regular expressions:

scan(text = chartr("[]", "  ", s), sep = ",", quiet = TRUE)

Upvotes: 3

akrun
akrun

Reputation: 886938

One option is to extract the numbers from the string using stri_extract (stringi package). The output of stri_extract_all is a list of vector with length 1. Usually, if there are multiple elements of 's' (here it is a single string), to convert it to a single vector, we use unlist and then wrap with as.integer. As there is only a single list element, we can extract that element with [[

library(stringi)
as.integer(stri_extract_all(s, regex = "\\d+")[[1]])

If we split up the code, as mentioned the stri_extract_all returns a list of length 1.

stri_extract_all(s, regex = "\\d+")
#[[1]]####
#[1] "14" "7"  "5"  "3"  "4"  "0"  "1"  "7"  "2"  "3"  "1"  "18" "13" "4"  "23" "7"  "8"  "8"  "11" "18" "15" "6"  "2"  "10"
#[25] "2"  "4"  "8"  "5"  "11" "5"  "1"  "5"  "2"  "4"  "3"  "1"  "6"  "8"  "5"  "5"  "3"  "1"  "1"  "4"  "5"  "2"  "9"  "3" 
#[49] "4"  "11" "11" "14" "3"  "12" "2"  "6"  "0"  "0"  "15" "1"  "18" "5"  "3"  "6"  "6"  "6"

Extract the list element containing the vector

stri_extract_all(s, regex = "\\d+")[[1]]
#[1] "14" "7"  "5"  "3"  "4"  "0"  "1"  "7"  "2"  "3"  "1"  "18" "13" "4"  "23" "7"  "8"  "8"  "11" "18" "15" "6"  "2"  "10"
#[25] "2"  "4"  "8"  "5"  "11" "5"  "1"  "5"  "2"  "4"  "3"  "1"  "6"  "8"  "5"  "5"  "3"  "1"  "1"  "4"  "5"  "2"  "9"  "3" 
#[49] "4"  "11" "11" "14" "3"  "12" "2"  "6"  "0"  "0"  "15" "1"  "18" "5"  "3"  "6"  "6"  "6"

and then convert the vector of character elements to integer

Upvotes: 1

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