stri_subset: Select Elements that Match a Given Pattern¶

Description¶

These functions return or modify a sub-vector where there is a match to a given pattern. In other words, they are roughly equivalent (but faster and easier to use) to a call to str[stri_detect(str, ...)] or str[stri_detect(str, ...)] <- value.

Usage¶

stri_subset(str, ..., regex, fixed, coll, charclass)

stri_subset(str, ..., regex, fixed, coll, charclass) <- value

stri_subset_fixed(
  str,
  pattern,
  omit_na = FALSE,
  negate = FALSE,
  ...,
  opts_fixed = NULL
)

stri_subset_fixed(str, pattern, negate=FALSE, ..., opts_fixed=NULL) <- value

stri_subset_charclass(str, pattern, omit_na = FALSE, negate = FALSE)

stri_subset_charclass(str, pattern, negate=FALSE) <- value

stri_subset_coll(
  str,
  pattern,
  omit_na = FALSE,
  negate = FALSE,
  ...,
  opts_collator = NULL
)

stri_subset_coll(str, pattern, negate=FALSE, ..., opts_collator=NULL) <- value

stri_subset_regex(
  str,
  pattern,
  omit_na = FALSE,
  negate = FALSE,
  ...,
  opts_regex = NULL
)

stri_subset_regex(str, pattern, negate=FALSE, ..., opts_regex=NULL) <- value

Arguments¶


`str`	character vector; strings to search within
`...`	supplementary arguments passed to the underlying functions, including additional settings for `opts_collator`, `opts_regex`, `opts_fixed`, and so on
`value`	non-empty character vector of replacement strings; replacement function only
`pattern`, `regex`, `fixed`, `coll`, `charclass`	character vector; search patterns (no more than the length of `str`); for more details refer to stringi-search
`omit_na`	single logical value; should missing values be excluded from the result?
`negate`	single logical value; whether a no-match is rather of interest
`opts_collator`, `opts_fixed`, `opts_regex`	a named list used to tune up the search engine’s settings; see `stri_opts_collator`, `stri_opts_fixed`, and `stri_opts_regex`, respectively; `NULL` for the defaults

Details¶

Vectorized over str as well as partially over pattern and value, with recycling of the elements in the shorter vector if necessary. As the aim here is to subset str, pattern cannot be longer than the former. Moreover, if the number of items to replace is not a multiple of length of value, a warning is emitted and the unused elements are ignored. Hence, the length of the output will be the same as length of str.

stri_subset and stri_subset<- are convenience functions. They call either stri_subset_regex, stri_subset_fixed, stri_subset_coll, or stri_subset_charclass, depending on the argument used.

Value¶

The stri_subset_* functions return a character vector. As usual, the output encoding is UTF-8.

The stri_subset_*<- functions modifies str ‘in-place’.

Author(s)¶

Marek Gagolewski and other contributors

Examples¶

stri_subset_regex(c('stringi R', '123', 'ID456', ''), '^[0-9]+$')
## [1] "123"
x <- c('stringi R', '123', 'ID456', '')
`stri_subset_regex<-`(x, '[0-9]+$', negate=TRUE, value=NA)  # returns a copy
## [1] NA      "123"   "ID456" NA
stri_subset_regex(x, '[0-9]+$') <- NA  # modifies `x` in-place
print(x)
## [1] "stringi R" NA          NA          ""