valuetype.Rd
Pattern matching in quanteda using the valuetype
argument.
valuetype | the type of pattern matching: |
---|
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 also
glob2rx
and References below.
"regex"
Regular expression matching.
"fixed"
Fixed (literal) pattern matching.
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 glob2rx) when
they contain wild card characters, and to fixed pattern matches when they
do not.