Select Elements that Match a Given Pattern

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

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'.

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.

Author

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          ""