Stemmer Construction
Make a stemmer from a set of (term, stem) pairs.
new_stemmer(term, stem, default = NULL, duplicates = "first",
vectorize = TRUE)term |
character vector of terms to stem. |
stem |
character vector the same length as |
default |
if non- |
duplicates |
action to take for duplicates in the |
.
vectorize |
whether to produce a vectorized stemmer that accepts and returns vector arguments. |
Giving a list of terms and a corresponding list of stems, this produces a
function that maps terms to their corresponding entry. If
default = NULL, then values absent from the term argument
get left as-is; otherwise, they get replaced by the default value.
The duplicates argument indicates the action to take if
there are duplicate entries in the term argument:
duplicates = "first" take the first matching entry in the
stem list.
duplicates = "last" take the last matching entry in the
stem list.
duplicates = "omit" use the default value for
duplicated terms.
duplicates = "fail" raise an error if there are duplicated
terms.
By default, with vectorize = TRUE, the resulting stemmer accepts a
character vector as input and returns a character vector of the same length
with entries giving the stems of the corresponding input entries.
Setting vectorize = FALSE gives a function that accepts a single input
and returns a single output. This can be more efficient when used as part of
a text_filter.
# map uppercase to lowercase, leave others unchanged
stemmer <- new_stemmer(LETTERS, letters)
stemmer(c("A", "E", "I", "O", "U", "1", "2", "3"))
# map uppercase to lowercase, drop others
stemmer <- new_stemmer(LETTERS, letters, default = NA)
stemmer(c("A", "E", "I", "O", "U", "1", "2", "3"))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.