valuetype {quanteda} | R Documentation |
Pattern matching using valuetype
Description
Pattern matching in quanteda using the valuetype
argument.
Arguments
valuetype |
the type of pattern matching: |
case_insensitive |
logical; if |
Details
Pattern matching in in quanteda uses "glob"-style pattern
matching as the default, because this is simpler than regular expression
matching while addressing most users' needs. It is also has the advantage
of being identical to fixed pattern matching when the wildcard characters
(*
and ?
) are not used. Finally, most dictionary formats use glob
matching.
"glob"
"glob"-style wildcard expressions, the quanteda default. The implementation used in quanteda uses
*
to match any number of any characters including none, and?
to match any single character. See alsoutils::glob2rx()
and References below."regex"
Regular expression matching.
"fixed"
Fixed (literal) pattern matching.
Note
If "fixed" is used with case_insensitive = TRUE
, features will
typically be lowercased internally prior to matching. Also, glob matches
are converted to regular expressions (using utils::glob2rx()
) when
they contain wild card characters, and to fixed pattern matches when they
do not.
See Also
utils::glob2rx()
, glob pattern matching (Wikipedia),
stringi::stringi-search-regex()
, stringi::stringi-search-fixed()