quanteda: char_select – R documentation

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char_select

Select or remove elements from a character vector

Description

These function select or discard elements from a character object. For convenience, the functions char_remove and char_keep are defined as shortcuts for char_select(x, pattern, selection = "remove") and char_select(x, pattern, selection = "keep"), respectively.

These functions make it easy to change, for instance, stopwords based on pattern matching.

Usage

char_select(
  x,
  pattern,
  selection = c("keep", "remove"),
  valuetype = c("glob", "fixed", "regex"),
  case_insensitive = TRUE
)

char_remove(x, ...)

char_keep(x, ...)

Arguments

`x`	an input character vector
`pattern`	a character vector, list of character vectors, dictionary, or collocations object. See pattern for details.
`selection`	whether to `"keep"` or `"remove"` the tokens matching `pattern`
`valuetype`	the type of pattern matching: `"glob"` for "glob"-style wildcard expressions; `"regex"` for regular expressions; or `"fixed"` for exact matching. See valuetype for details.
`case_insensitive`	logical; if `TRUE`, ignore case when matching a `pattern` or dictionary values
`...`	additional arguments passed by `char_remove` and `char_keep` to `char_select`. Cannot include `selection`.

Value

a modified character vector

Examples

# character selection
mykeywords <- c("natural", "national", "denatured", "other")
char_select(mykeywords, "nat*", valuetype = "glob")
char_select(mykeywords, "nat", valuetype = "regex")
char_select(mykeywords, c("natur*", "other"))
char_select(mykeywords, c("natur*", "other"), selection = "remove")

# character removal
char_remove(letters[1:5], c("a", "c", "x"))
words <- c("any", "and", "Anna", "as", "announce", "but")
char_remove(words, "an*")
char_remove(words, "an*", case_insensitive = FALSE)
char_remove(words, "^.n.+$", valuetype = "regex")

# remove some of the system stopwords
stopwords("en", source = "snowball")[1:6]
stopwords("en", source = "snowball")[1:6] %>%
  char_remove(c("me", "my*"))
  
# character keep
char_keep(letters[1:5], c("a", "c", "x"))

quanteda

Quantitative Analysis of Textual Data

v3.0.0

GPL-3

Authors

Kenneth Benoit [cre, aut, cph] (<https://orcid.org/0000-0002-0797-564X>), Kohei Watanabe [aut] (<https://orcid.org/0000-0001-6519-5265>), Haiyan Wang [aut] (<https://orcid.org/0000-0003-4992-4311>), Paul Nulty [aut] (<https://orcid.org/0000-0002-7214-4666>), Adam Obeng [aut] (<https://orcid.org/0000-0002-2906-4775>), Stefan Müller [aut] (<https://orcid.org/0000-0002-6315-4125>), Akitaka Matsuo [aut] (<https://orcid.org/0000-0002-3323-6330>), William Lowe [aut] (<https://orcid.org/0000-0002-1549-6163>), Christian Müller [ctb], European Research Council [fnd] (ERC-2011-StG 283794-QUANTESS)

Initial release