So I have a table in R, and an example of of the string I am trying to capture is this:
C.Hale (79-83)
I want to write a regular expression to extract the (79-83).
How do I go about doing this?
We can use sub. We match one or more characters that are not a space ([^ ]+) from the beginning of the string (^) , followed by a space (\\s) and replace it with a ''.
sub('^[^ ]+\\s', '', str1)
#[1] "(79-83)"
Or another option is stri_extract_all from stringi
library(stringi)
stri_extract_all_regex(str1, '\\([^)]+\\)')[[1]]
#[1] "(79-83)"
data
str1 <- 'C.Hale (79-83)'
One possibility using the qdapRegex package I maintain:
x <- "C.Hale (79-83)"
library(qdapRegex)
rm_round(x, extract = TRUE, include.markers = TRUE)
## [[1]]
## [1] "(79-83)"
Related
I have been trying to extract a portion of string after the occurrence of a first ^ sign. For example, the string looks like abc^28092015^def^1234. I need to extract 28092015 sandwiched between the 1st two ^ signs.
So, I need to extract 8 characters from the occurrence of the 1st ^ sign. I have been trying to extract the position of the first ^ sign and then use it as an argument in the substr function.
I tried to use this:
x=abc^28092015^def^1234 `rev(gregexpr("\\^", x)[[1]])[1]`
Referring the answer discussed here.
But it continues to return the last position. Can anyone please help me out?
I would use sub.
x <- "^28092015^def^1234"
sub("^.*?\\^(.*?)\\^.*", "\\1", x)
# [1] "28092015"
Since ^ is a special char in regex, you need to escape that in-order to match literal ^ symbols.
or
Do splitting on ^ and get the value of second index.
strsplit(x,"^", fixed=-T)[[1]][2]
# [1] "28092015"
or
You may use gsub aslo.
gsub("^.*?\\^|\\^.*", "", x, perl=T)
# [1] "28092015"
Here's one option with base R:
x <- "abc^28092015^def^1234"
m <- regexpr("(?<=\\^)(.+?)(?=\\^)", x, perl = TRUE)
##
R> regmatches(x, m)
#[1] "28092015"
Another option is stri_extract_first from library(stringi)
library(stringi)
stri_extract_first_regex(str1, '(?<=\\^)\\d+(?=\\^)')
#[1] "28092015"
If it is any character between two ^
stri_extract(str1, regex='(?<=\\^)[^^]+')
#[1] "28092015"
data
str1 <- 'abc^28092015^def^1234'
x <- 'abc^28092015^def^1234'
library(qdapRegex)
unlist(rm_between(x, '^', '^', extract=TRUE))[1]
# [1] "28092015"
It would be better if you split it using ^. But if you still want the pattern, you can try this.
^\S+\^(\d+)(?=\^)
Then match group 1.
OUTPUT
28092015
See DEMO
I have:
> pattern
[1] "(/[[:digit:]]{4}/)"
so I want to extract only the matching portions...the digits plus the /.../. Here's what I tried:
> gsub(pattern, '\\1', grep(pattern, c("t3tg3wgw/5764/", "ggg", "grsgs/gwgew/5656/bfsbs"), value=TRUE))
[1] "t3tg3wgw/5764/" "grsgs/gwgew/5656/bfsbs"
However this still returns letters attached to the actual match that do not themselves match the regex. How can I extract only /5764/ and /5656/?
We could extract the pattern / followed by one or more numbers ([0-9]+) followed by / using str_extract_all from library(stringr) to output a list, which can be unlisted to convert to vector
library(stringr)
unlist(str_extract_all(v1, '/[0-9]+/'))
#[1] "/5764/" "/5656/"
Or we use the same pattern and using regmatches/gregexpr from base R
unlist(regmatches(v1, gregexpr('/[0-9]+/',v1)))
#[1] "/5764/" "/5656/"
data
v1 <- c("t3tg3wgw/5764/", "ggg", "grsgs/gwgew/5656/bfsbs")
Try changing the pattern to .*(/[[:digit:]]{4}/).*
I have the following code:
input <- "1-FA-1-I2-1-I2-1-I2-1-EX-1-I2-1-I3-1-FA-1-I1-1-I2-1-TR-1-I1-1-I2-1-FA-1-I3-1-I1-1-FA-1-FA-1-NR-1-I3-1-I2-1-TR-1-I1-1-I2-1-I1-1-I2-1-FA-1-I2-1-I1-1-I3-1-FA-1-QU-1-I1-1-I2-1-I2-1-I2-1-NR-1-I2-1-I2-1-NR-1-I1-1-I2-1-I1-1-NR-1-I3-1-QU-1-I2-1-I3-1-QU-1-NR-1-I2-1-I1-1-NR-1-QU-1-QU-1-I2-1-I1-1-EX"
innovation_patterns <- gsub(input, pattern = "-1-", replacement = "-")
innovation_patterns <- lapply(innovation_patterns, str_extract_all, '(?:I\\d-?)*I3(?:-?I\\d)*')
This outputs:
"I2-I3" "I3-I1" "I3-I2" "I2-I1-I3" "I3" "I2-I3"
However, I only want to extract matches to the regex that are following immediately to a specific string, e.g.:
only match the regex when it's preceded by the literal string FA-I2-I2-I2-EX.
This, for example, would be the first match of the regex, while the second match is preceded by FA-I1-I2-TR-I1-I2-FA.
The expected output is roughly the same as in the regex above, but only selecting one of the 5 matches, because it needs to be preceded by a specific literal string.
How can I modify this regex to achieve this purpose? I assume it needs to use a positive lookbehind to first identify the literal string, then execute the regex.
I don't know if I'm fully understanding what you mean, but it seems you could use positive lookbehind.
For instance:
(?<=a)b (positive lookbehind) matches the b (and only the b) in cab, but does not match bed or debt
There should be something more intuitive but i think this will do the job
literal <- "FA-I2-I2-I2-EX"
innovation_patterns <- gsub(input, pattern = "-1-", replacement = "-")
a <- lapply(strsplit(innovation_patterns, literal )[[1]], str_extract_all, '(?:I\\d-?)*I3(?:-?I\\d)*')
b <- lapply(2:length(a), function(x){
a[[x]][[1]][1]
})
print(b)
Use (*SKIP)(*F)
innovation_patterns <- gsub(input, pattern = "-1-", replacement = "-")
innovation_patterns <- lapply(innovation_patterns, str_extract_all, perl('FA-I1-I2-TR-I1-I2-FA.*(*SKIP)(*F)|(?:I\\d-?)*I3(?:-?I\\d)*'))
Syntax would be like,
partIDontWant.*(*SKIP)(*F)|choose from the string which exists before partIDontWant
DEMO
Here's is another way you could go about this.
x <- "1-FA-1-I2-1-I2-1-I2-1-EX-1-I2-1-I3-1-FA-1-I1-1-I2-1-TR-1-I1-1-I2-1-FA-1-I3-1-I1-1-FA-1-FA-1-NR-1-I3-1-I2-1-TR-1-I1-1-I2-1-I1-1-I2-1-FA-1-I2-1-I1-1-I3-1-FA-1-QU-1-I1-1-I2-1-I2-1-I2-1-NR-1-I2-1-I2-1-NR-1-I1-1-I2-1-I1-1-NR-1-I3-1-QU-1-I2-1-I3-1-QU-1-NR-1-I2-1-I1-1-NR-1-QU-1-QU-1-I2-1-I1-1-EX"
CODE
substr <- 'FA-I2-I2-I2-EX'
regex <- paste0(substr, '-?((?:I\\d-?)*I3(?:-?I\\d)*)')
gsubfn::strapply(gsub('-1-', '-', x), regex, simplify = c)
## [1] "I2-I3"
Here's how to implement it:
lapply(innovation_patterns, str_extract_all, '(?<=FA-I2-I2-I2-EX-?)(?:I\\d-?)*I3(?:-?I\\d)*');
## [[1]]
## [[1]][[1]]
## [1] "I2-I3"
I try to use stringr package to extract part of a string, which is between two particular patterns.
For example, I have:
my.string <- "nanaqwertybaba"
left.border <- "nana"
right.border <- "baba"
and by the use of str_extract(string, pattern) function (where pattern is defined by a POSIX regular expression) I would like to receive:
"qwerty"
Solutions from Google did not work.
In base R you can use gsub. The parentheses in the pattern create numbered capturing groups. Here we select the second group in the replacement, i.e. the group between the borders. The . matches any character. The * means that there is zero or more of the preceeding element
gsub(pattern = "(.*nana)(.*)(baba.*)",
replacement = "\\2",
x = "xxxnanaRisnicebabayyy")
# "Risnice"
I do not know whether and how this is possible with functions provided by stringr but you can also use base regexpr and substring:
pattern <- paste0("(?<=", left.border, ")[a-z]+(?=", right.border, ")")
# "(?<=nana)[a-z]+(?=baba)"
rx <- regexpr(pattern, text=my.string, perl=TRUE)
# [1] 5
# attr(,"match.length")
# [1] 6
substring(my.string, rx, rx+attr(rx, "match.length")-1)
# [1] "qwerty"
I would use str_match from stringr: "str_match extracts capture groups formed by
() from the first match. It returns a character matrix with one column for the complete match and one column for each group." ref
str_match(my.string, paste(left.border, '(.+)', right.border, sep=''))[,2]
The code above creates a regular expression with paste concatenating the capture group (.+) that captures 1 or more characters, with left and right borders (no spaces between strings).
A single match is assumed. So, [,2] selects the second column from the matrix returned by str_match.
You can use the package unglue:
library(unglue)
my.string <- "nanaqwertybaba"
unglue_vec(my.string, "nana{res}baba")
#> [1] "qwerty"
I have a string:
s <- "test.test AS field1, ablh.blah AS field2, faslk.lsdf AS field3"
I want to convert to:
"field1, field2, field3"
I know that the regular expression (\w+)(?:,|$) will extract the strings I want ('field1,' etc) but I can't figure out how to extract it with gsub.
## Preparation
s <- "test.test AS field1, ablh.blah AS field2, faslk.lsdf AS field3"
pat <- "(\\w+)(?:,|$)" ## Note the doubly-escaped \\w
## Use the powerful gregexpr/regmatches one-two punch
m <- gregexpr(pat, s)
paste(regmatches(s, m)[[1]], collapse=" ")
# [1] "field1, field2, field3"
With strapplyc in the gsubfn package one can do it with a particularly simple regular expression which extracts each string of word characters that follows " AS " (If the field can contain non-word characters then replace \\w with the appropriate expression, for example any char that is not a space or comma: [^ ,]):
> library(gsubfn)
> strapplyc(s, " AS (\\w+)", simplify = toString)[[1]]
[1] "field1, field2, field3"