pattern {quanteda} | R Documentation |
Pattern for feature, token and keyword matching
Description
Pattern(s) for use in matching features, tokens, and keywords through a valuetype pattern.
Arguments
pattern |
a character vector, list of character vectors, dictionary, or collocations object. See pattern for details. |
Details
The pattern
argument is a vector of patterns, including
sequences, to match in a target object, whose match type is specified by
valuetype. Note that an empty pattern (""
) will match
"padding" in a tokens object.
character
A character vector of token patterns to be selected or removed. Whitespace is not privileged, so that in a character vector, white space is interpreted literally. If you wish to consider whitespace-separated elements as sequences of tokens, wrap the argument in
phrase()
.list of character objects
If the list elements are character vectors of length 1, then this is equivalent to a vector of characters. If a list element contains a vector of characters longer than length 1, then for matching will consider these as sequences of matches, equivalent to wrapping the argument in
phrase()
, except for matching to dfm features where this does not apply.dictionary
Values in dictionary are used as patterns, for literal matches. Multi-word values are automatically converted into phrases, so performing selection or compounding using a dictionary is the same as wrapping the dictionary in
phrase()
.collocations
Collocations objects created from
quanteda.textstats::textstat_collocations()
, which are treated as phrases automatically.
See Also
Examples
# these are interpreted literally
(patt1 <- c("president", "white house", "house of representatives"))
# as multi-word sequences
phrase(patt1)
# three single-word patterns
(patt2 <- c("president", "white_house", "house_of_representatives"))
phrase(patt2)
# this is equivalent to phrase(patt1)
(patt3 <- list(c("president"), c("white", "house"),
c("house", "of", "representatives")))
# glob expression can be used
phrase(patt4 <- c("president?", "white house", "house * representatives"))
# this is equivalent to phrase(patt4)
(patt5 <- list(c("president?"), c("white", "house"), c("house", "*", "representatives")))
# dictionary with multi-word matches
(dict1 <- dictionary(list(us = c("president", "white house", "house of representatives"))))
phrase(dict1)