stri_extract: Extract Pattern Occurrences¶
Description¶
These functions extract all substrings matching a given pattern.
stri_extract_all_* extracts all the matches. stri_extract_first_* and stri_extract_last_* yield the first or the last matches, respectively.
Usage¶
stri_extract_all(str, ..., regex, fixed, coll, charclass)
stri_extract_first(str, ..., regex, fixed, coll, charclass)
stri_extract_last(str, ..., regex, fixed, coll, charclass)
stri_extract(
str,
...,
regex,
fixed,
coll,
charclass,
mode = c("first", "all", "last")
)
stri_extract_all_charclass(
str,
pattern,
merge = TRUE,
simplify = FALSE,
omit_no_match = FALSE
)
stri_extract_first_charclass(str, pattern)
stri_extract_last_charclass(str, pattern)
stri_extract_all_coll(
str,
pattern,
simplify = FALSE,
omit_no_match = FALSE,
...,
opts_collator = NULL
)
stri_extract_first_coll(str, pattern, ..., opts_collator = NULL)
stri_extract_last_coll(str, pattern, ..., opts_collator = NULL)
stri_extract_all_regex(
str,
pattern,
simplify = FALSE,
omit_no_match = FALSE,
...,
opts_regex = NULL
)
stri_extract_first_regex(str, pattern, ..., opts_regex = NULL)
stri_extract_last_regex(str, pattern, ..., opts_regex = NULL)
stri_extract_all_fixed(
str,
pattern,
simplify = FALSE,
omit_no_match = FALSE,
...,
opts_fixed = NULL
)
stri_extract_first_fixed(str, pattern, ..., opts_fixed = NULL)
stri_extract_last_fixed(str, pattern, ..., opts_fixed = NULL)
Arguments¶
|
character vector; strings to search in |
|
supplementary arguments passed to the underlying functions, including additional settings for |
|
single string; one of: |
|
character vector; search patterns; for more details refer to stringi-search |
|
single logical value; indicates whether consecutive pattern matches will be merged into one string; |
|
single logical value; if |
|
single logical value; if |
|
a named list to tune up the search engine’s settings; see |
Details¶
Vectorized over str and pattern (with recycling of the elements in the shorter vector if necessary). This allows to, for instance, search for one pattern in each given string, search for each pattern in one given string, and search for the i-th pattern within the i-th string.
Check out stri_match for the extraction of matches to individual regex capture groups.
stri_extract, stri_extract_all, stri_extract_first, and stri_extract_last are convenience functions. They merely call stri_extract_*_*, depending on the arguments used.
Value¶
For stri_extract_all*, if simplify=FALSE (the default), then a list of character vectors is returned. Each list element represents the results of a different search scenario. If a pattern is not found and omit_no_match=FALSE, then a character vector of length 1 with single NA value will be generated.
Otherwise, i.e., if simplify is not FALSE, then stri_list2matrix with byrow=TRUE argument is called on the resulting object. In such a case, the function yields a character matrix with an appropriate number of rows (according to the length of str, pattern, etc.). Note that stri_list2matrix’s fill argument is set either to an empty string or NA, depending on whether simplify is TRUE or NA, respectively.
stri_extract_first* and stri_extract_last* return a character vector. A NA element indicates a no-match.
Note that stri_extract_last_regex searches from start to end, but skips overlapping matches, see the example below.
See Also¶
The official online manual of stringi at https://stringi.gagolewski.com/
Gagolewski M., stringi: Fast and portable character string processing in R, Journal of Statistical Software 103(2), 2022, 1-59, doi:10.18637/jss.v103.i02
Other search_extract: about_search, stri_extract_all_boundaries(), stri_match_all()
Examples¶
stri_extract_all('XaaaaX', regex=c('\\p{Ll}', '\\p{Ll}+', '\\p{Ll}{2,3}', '\\p{Ll}{2,3}?'))
## [[1]]
## [1] "a" "a" "a" "a"
##
## [[2]]
## [1] "aaaa"
##
## [[3]]
## [1] "aaa"
##
## [[4]]
## [1] "aa" "aa"
stri_extract_all('Bartolini', coll='i')
## [[1]]
## [1] "i" "i"
stri_extract_all('stringi is so good!', charclass='\\p{Zs}') # all white-spaces
## [[1]]
## [1] " " " " " "
stri_extract_all_charclass(c('AbcdeFgHijK', 'abc', 'ABC'), '\\p{Ll}')
## [[1]]
## [1] "bcde" "g" "ij"
##
## [[2]]
## [1] "abc"
##
## [[3]]
## [1] NA
stri_extract_all_charclass(c('AbcdeFgHijK', 'abc', 'ABC'), '\\p{Ll}', merge=FALSE)
## [[1]]
## [1] "b" "c" "d" "e" "g" "i" "j"
##
## [[2]]
## [1] "a" "b" "c"
##
## [[3]]
## [1] NA
stri_extract_first_charclass('AaBbCc', '\\p{Ll}')
## [1] "a"
stri_extract_last_charclass('AaBbCc', '\\p{Ll}')
## [1] "c"
## Not run:
# emoji support available since ICU 57
stri_extract_all_charclass(stri_enc_fromutf32(32:55200), '\\p{EMOJI}')
## [[1]]
## [1] "#" "*"
## [3] "0123456789" "©"
## [5] "®" "‼"
## [7] "⁉" "™"
## [9] "ℹ" "↔↕↖↗↘↙"
## [11] "↩↪" "⌚⌛"
## [13] "⌨" "⏏"
## [15] "⏩⏪⏫⏬⏭⏮⏯⏰⏱⏲⏳" "⏸⏹⏺"
## [17] "Ⓜ" "▪▫"
## [19] "▶" "◀"
## [21] "◻◼◽◾" "☀☁☂☃☄"
## [23] "☎" "☑"
## [25] "☔☕" "☘"
## [27] "☝" "☠"
## [29] "☢☣" "☦"
## [31] "☪" "☮☯"
## [33] "☸☹☺" "♀"
## [35] "♂" "♈♉♊♋♌♍♎♏♐♑♒♓"
## [37] "♟♠" "♣"
## [39] "♥♦" "♨"
## [41] "♻" "♾♿"
## [43] "⚒⚓⚔⚕⚖⚗" "⚙"
## [45] "⚛⚜" "⚠⚡"
## [47] "⚧" "⚪⚫"
## [49] "⚰⚱" "⚽⚾"
## [51] "⛄⛅" "⛈"
## [53] "⛎⛏" "⛑"
## [55] "⛓⛔" "⛩⛪"
## [57] "⛰⛱⛲⛳⛴⛵" "⛷⛸⛹⛺"
## [59] "⛽" "✂"
## [61] "✅" "✈✉✊✋✌✍"
## [63] "✏" "✒"
## [65] "✔" "✖"
## [67] "✝" "✡"
## [69] "✨" "✳✴"
## [71] "❄" "❇"
## [73] "❌" "❎"
## [75] "❓❔❕" "❗"
## [77] "❣❤" "➕➖➗"
## [79] "➡" "➰"
## [81] "➿" "⤴⤵"
## [83] "⬅⬆⬇" "⬛⬜"
## [85] "⭐" "⭕"
## [87] "〰" "〽"
## [89] "㊗" "㊙"
## End(Not run)
stri_extract_all_coll(c('AaaaaaaA', 'AAAA'), 'a')
## [[1]]
## [1] "a" "a" "a" "a" "a" "a"
##
## [[2]]
## [1] NA
stri_extract_first_coll(c('Yy\u00FD', 'AAA'), 'y', strength=2, locale='sk_SK')
## [1] "Y" NA
stri_extract_last_coll(c('Yy\u00FD', 'AAA'), 'y', strength=1, locale='sk_SK')
## [1] "ý" NA
stri_extract_all_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+', '\\p{Ll}{2,3}', '\\p{Ll}{2,3}?'))
## [[1]]
## [1] "a" "a" "a" "a"
##
## [[2]]
## [1] "aaaa"
##
## [[3]]
## [1] "aaa"
##
## [[4]]
## [1] "aa" "aa"
stri_extract_first_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+', '\\p{Ll}{2,3}', '\\p{Ll}{2,3}?'))
## [1] "a" "aaaa" "aaa" "aa"
stri_extract_last_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+', '\\p{Ll}{2,3}', '\\p{Ll}{2,3}?'))
## [1] "a" "aaaa" "aaa" "aa"
stri_list2matrix(stri_extract_all_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+')))
## [,1] [,2]
## [1,] "a" "aaaa"
## [2,] "a" NA
## [3,] "a" NA
## [4,] "a" NA
stri_extract_all_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+'), simplify=TRUE)
## [,1] [,2] [,3] [,4]
## [1,] "a" "a" "a" "a"
## [2,] "aaaa" "" "" ""
stri_extract_all_regex('XaaaaX', c('\\p{Ll}', '\\p{Ll}+'), simplify=NA)
## [,1] [,2] [,3] [,4]
## [1,] "a" "a" "a" "a"
## [2,] "aaaa" NA NA NA
stri_extract_all_fixed('abaBAba', 'Aba', case_insensitive=TRUE)
## [[1]]
## [1] "aba" "Aba"
stri_extract_all_fixed('abaBAba', 'Aba', case_insensitive=TRUE, overlap=TRUE)
## [[1]]
## [1] "aba" "aBA" "Aba"
# Searching for the last occurrence:
# Note the difference - regex searches left to right, with no overlaps.
stri_extract_last_fixed("agAGA", "aga", case_insensitive=TRUE)
## [1] "AGA"
stri_extract_last_regex("agAGA", "aga", case_insensitive=TRUE)
## [1] "agA"