CODEWITHSUNDEEP
rregexpattern-matchingstringr
learning_to_code
learning_to_code

Reputation: 69

Extract text in two columns from a string

I have a table where one column has data like this:

table$test_string<- "[projectname](https://somewebsite.com/projectname/Abc/xyz-09)"

1.) I am trying to extract the first part of this string within the square brackets in one column, i.e.

table$project_name <- "projectname"

using the regex:

project_name <- "^\\[|(?:[a-zA-Z]|[0-9])+|\\]$"
table$project_name <- str_extract(table$test_string, project_name)

If I test the regex on 1 value (1 row individually) of the table, the above regex works with using str_extract_all(table$test_string, project_name[[1]][2]).

However, I get NA when I apply the regex pattern to the whole table and an error if I use str_extract_all.

2.) Second part of the string, which is a URL in another column,

table$url_link <- "https://somewebsite.com/projectname/Abc/xyz-09"

I am using the following regex expression for URL:

url_pattern <- "http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\\(\\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+"

table$url_link <- str_extract(table$test_string, url_pattern)

and this works on the whole table, however, I still get the ')' last paranthesis in the url link.

What am I missing here? and why does the first regex work individually and not on the whole table? and for the url, how do I not get the last paranthesis?

Upvotes: 0

Views: 138

Answers (2)

akrun
akrun

Reputation: 887118

We can make use of convenient functions from qdapRegex

library(qdapRegex)
rm_round(test_string, extract = TRUE)[[1]]
#[1] "https://somewebsite.com/projectname/Abc/xyz-09"

rm_square(test_string, extract = TRUE)[[1]]
#[1] "projectname"

data

test_string<- "[projectname](https://somewebsite.com/projectname/Abc/xyz-09)"

Upvotes: 0

Vincent
Vincent

Reputation: 17715

It feels like you could simplify things considerably by using parentheses to group capture. For example:

test_string<- "[projectname](https://somewebsite.com/projectname/Abc/xyz-09)"

regex <- "\\[(.*)\\]\\((.*)\\)"

gsub(regex, "\\1", test_string)
#> [1] "projectname"

gsub(regex, "\\2", test_string)
#> [1] "https://somewebsite.com/projectname/Abc/xyz-09"

Upvotes: 3

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