For example, this is my string -> abcd 1234abcda="author 1" content="author 2.">\n
I only want the string author 2. by using the function str_extract() in R. How can I use regex to do that? Thank you so much.
You can use :
string = 'abcd 1234abcda="author 1" content="author 2.">\n'
sub('.*"(.*)".*', '\\1', string)
#[1] "author 2."
With str_match
library(stringr)
str_match(string, '.*"(.*)"')[, 2]
Another option is to extract all the values with "author" followed by a number and select the last one using tail.
tail(str_extract_all(string, 'author \\d+')[[1]], 1)
Related
I'm trying to split a string containing two entries and each entry has a specific format:
Category (e.g. active site/region) which is followed by a :
Term (e.g. His, Glu/nucleotide-binding motif A) which is followed by a ,
Here's the string that I want to split:
string <- "active site: His, Glu,region: nucleotide-binding motif A,"
This is what I have tried so far. Except for the two empty substrings, it produces the desired output.
unlist(str_extract_all(string, ".*?(?=,(?:\\w+|$))"))
[1] "active site: His, Glu" "" "region: nucleotide-binding motif A"
[4] ""
How do I get rid of the empty substrings?
You get the empty strings because .*? can also match an empty string where this assertion (?=,(?:\\w+|$)) is true
You can exclude matching a colon or comma using a negated character class before matching :
[^:,\n]+:.*?(?=,(?:\w|$))
Explanation
[^:,\n]+ Match 1+ chars other than : , or a newline
: Match the colon
.*? Match any char as least as possbiel
(?= Positive lookahead, assert that what is directly to the right from the current position:
, Match literally
(?:\w|$) Match either a single word char, or assert the end of the string
) Close the lookahead
Regex demo | R demo
string <- "active site: His, Glu,region: nucleotide-binding motif A,"
unlist(str_extract_all(string, "[^:,\\n]+:.*?(?=,(?:\\w|$))"))
Output
[1] "active site: His, Glu" "region: nucleotide-binding motif A"
Much longer and not as elegant as #The fourth bird +1,
but it works:
library(stringr)
string2 <- strsplit(string, "([^,]+,[^,]+),", perl = TRUE)[[1]][2]
string1 <- str_replace(string, string2, "")
string <- str_replace_all(c(string1, string2), '\\,$', '')
> string
[1] "active site: His, Glu"
[2] "region: nucleotide-binding motif A"
Assuming I have the following string:
string = "path/stack/over_flow/Pedro_account"
I am intrested in matching the first 2 characters after the last / and before the first _. So in this case the desired out put is:
Pe
What I have so far is a mix of substr and str_extract:
substr(str_extract(string, "[^/]*$"),1,2)
which of course will give an answer but I belive there is a nice regex for it as well, and that is what I'm looking for.
You can use
library(stringr)
str_extract(string, "(?<=/)[^/]{2}(?=[^/]*$)")
## => [1] "Pe"
See the R demo and the regex demo. Details:
(?<=/) - a location immediately preceded with a / char
[^/]{2} - two chars other than /
(?=[^/]*$) - a location immediately preceded with zero or more chars other than / till the end of string.
Using basename to get the last folder name, then substring:
substr(basename("path/stack/over_flow/Pedro_account"), 1, 2)
# [1] "Pe"
Remove everything till last / and extract first 2 characters.
Base R -
string = "path/stack/over_flow/Pedro_account"
substr(sub('.*/', '', string), 1, 2)
#[1] "Pe"
stringr
substr(stringr::str_remove(string, '.*/'), 1, 2)
You can use str_match with a capture group:
/ Match literally
([^/_]{2}) Capture 2 chars other than / or _ in group 1
[^/]* Match optional chars other than /
$ End of string
See a regex demo and a R demo.
Example
library(stringr)
string = "path/stack/over_flow/Pedro_account"
str_match(string, "/([^/_]{2})[^/]*$")[,2]
Output
[1] "Pe"
I would like to insert characters in the places were a string change its case. I tried this to insert a '\n' after a fixed number of characters and then a ' ', as I don't figure out how to detect the case change
s <-c("FloridaIslandE7", "FloridaIslandE9", "Meta")
gsub('^(.{7})(.{6})(.*)$', '\\1\\\n\\2 \\3', s )
[1] "Florida\nIsland E7" "Florida\nIsland E9" "Meta"
This works because the positions are fixed but I would like to know how to do it for the general case.
Surely there's a less convoluted regex for this, but you could try:
gsub('([A-Z][0-9])', ' \\1', gsub('([a-z])([A-Z])', '\\1\n\\2', s))
Output:
[1] "Florida\nIsland E7" "Florida\nIsland E9" "Meta"
Here is an option
str_replace_all(s, "(?<=[a-z])(?=[A-Z])", "\n")
#[1] "Florida\nIsland\nE7" "Florida\nIsland\nE9" "Meta"
If you really want to insert \n, try this:
gsub("([a-z])([A-Z])", "\\1\\\n\\2", s)
[1] "Florida\nIsland\nE7" "Florida\nIsland\nE9" "Meta"
Thank you in advance for any feedback.
I am attempting to clean some data in R where a time stamp and a text string are included together in the same cell. I am not getting the expected result. I know the regex needs validation work, but just testing out this particular function
Expected:
"04/05/2018 17:14:35" " -(Additional comments) update"
Actual:
"04/05/2018 17:14:35 -(Additional comments) update"
What I tried:
string <- "04/05/2018 17:14:35 -(Additional comments) update"
pattern <- "[:digit:][:digit:][:punct:]
[:digit:][:digit:][:punct:]
[:digit:][:digit:][:digit:][:digit:]
[[:space:]]
[:digit:][:digit:]
[:punct:]
[:digit:][:digit:]
[:punct:]
[:digit:][:digit:]"
strsplit(string, pattern)
I also tried this variation, same result
pattern <- "[:digit:][:digit:]\\/
[:digit:][:digit:]\\/
[:digit:][:digit:][:digit:][:digit:]
[[:space:]]
[:digit:][:digit:]
\\:
[:digit:][:digit:]
\\:
[:digit:][:digit:]"
You can try :
string <- "04/05/2018 17:14:35 -(Additional comments) update"
gsub("(\\d{2}/\\d{2}/\\d{4} \\d{2}:\\d{2}:\\d{2}).*","\\1", string)
#[1] "04/05/2018 17:14:35"
#RHS part
gsub("(\\d{2}/\\d{2}/\\d{4} \\d{2}:\\d{2}:\\d{2})(.*)","\\2", string)
#" -(Additional comments) update"
Regex explanation:
\\d{2} - 2 digits
\\d{4} - 4 digits
/ - separator
: - separator
() - Group for selection
.* - Followed by anything
Seems OP is very keen on using strsplit. One option could be as:
strsplit(gsub("(\\d{2}/\\d{2}/\\d{4} \\d{2}:\\d{2}:\\d{2})(.*)",
paste("\\1","####","\\2",sep=""), string), split = "####")
# [[1]]
# [1] "04/05/2018 17:14:35" " -(Additional comments) update"
Try this:
sub('-.*','',string)
[1] "04/05/2018 17:14:35 "
string = 'Hello, how are you?'
What I want to achieve:
Hello\\W how are you\\W
What I've done: Substituting all characters that are not alphanumeric with '\\W'
gsub('(\\W)+[^\\S]+','\\\\W',string,perl=TRUE)
[1] "Hello\\Whow are you?"
I'm not too sure why wasn't the question mark at the end of the sentence substituted with '\\W'and why was the first space being substituted. Could anyone help me out with this? Thank you!
We can do
gsub("[,?]", "\\\\W", string)
#[1] "Hello\\W how are you\\W"
If there are other characters, use [[:punct:]]
gsub("[[:punct:]]", "\\\\W", string)
#[1] "Hello\\W how are you\\W"