stri_startswith | R Documentation |
These functions check if a string starts or ends with a match to a given pattern. Also, it is possible to check if there is a match at a specific position.
stri_startswith(str, ..., fixed, coll, charclass)
stri_endswith(str, ..., fixed, coll, charclass)
stri_startswith_fixed(
str,
pattern,
from = 1L,
negate = FALSE,
...,
opts_fixed = NULL
)
stri_endswith_fixed(
str,
pattern,
to = -1L,
negate = FALSE,
...,
opts_fixed = NULL
)
stri_startswith_charclass(str, pattern, from = 1L, negate = FALSE)
stri_endswith_charclass(str, pattern, to = -1L, negate = FALSE)
stri_startswith_coll(
str,
pattern,
from = 1L,
negate = FALSE,
...,
opts_collator = NULL
)
stri_endswith_coll(
str,
pattern,
to = -1L,
negate = FALSE,
...,
opts_collator = NULL
)
str |
character vector |
... |
supplementary arguments passed to the underlying functions,
including additional settings for |
pattern , fixed , coll , charclass |
character vector defining search patterns; for more details refer to stringi-search |
from |
integer vector |
negate |
single logical value; whether a no-match to a pattern is rather of interest |
to |
integer vector |
opts_collator , opts_fixed |
a named list used to tune up
the search engine's settings; see |
Vectorized over str
, pattern
,
and from
or to
(with recycling
of the elements in the shorter vector if necessary).
If pattern
is empty, then the result is NA
and a warning is generated.
Argument start
controls the start position in str
where there is a match to a pattern
.
to
gives the end position.
Indexes given by from
or to
are of course 1-based,
i.e., an index 1 denotes the first character
in a string. This gives a typical R look-and-feel.
For negative indexes in from
or to
, counting starts
at the end of the string. For instance, index -1 denotes the last code point
in the string.
If you wish to test for a pattern match at an arbitrary
position in str
, use stri_detect
.
stri_startswith
and stri_endswith
are convenience functions.
They call either stri_*_fixed
, stri_*_coll
,
or stri_*_charclass
, depending on the argument used.
Relying on these underlying functions directly will make your code run
slightly faster.
Note that testing for a pattern match at the start or end of a string
has not been implemented separately for regex patterns.
For that you may use the '^
' and '$
' meta-characters,
see stringi-search-regex.
Each function returns a logical vector.
Marek Gagolewski and other contributors
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, \Sexpr[results=rd]{tools:::Rd_expr_doi("10.18637/jss.v103.i02")}
Other search_detect:
about_search
,
stri_detect()
stri_startswith_charclass(' trim me! ', '\\p{WSpace}')
stri_startswith_fixed(c('a1', 'a2', 'b3', 'a4', 'c5'), 'a')
stri_detect_regex(c('a1', 'a2', 'b3', 'a4', 'c5'), '^a')
stri_startswith_fixed('ababa', 'ba')
stri_startswith_fixed('ababa', 'ba', from=2)
stri_startswith_coll(c('a1', 'A2', 'b3', 'A4', 'C5'), 'a', strength=1)
pat <- stri_paste('\u0635\u0644\u0649 \u0627\u0644\u0644\u0647 ',
'\u0639\u0644\u064a\u0647 \u0648\u0633\u0644\u0645XYZ')
stri_endswith_coll('\ufdfa\ufdfa\ufdfaXYZ', pat, strength=1)
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