Filter Tokens Based on Term FrequencySource:
step_tokenfilter creates a specification of a recipe step that will
token variable to be filtered based on frequency.
step_tokenfilter( recipe, ..., role = NA, trained = FALSE, columns = NULL, max_times = Inf, min_times = 0, percentage = FALSE, max_tokens = 100, filter_fun = NULL, res = NULL, skip = FALSE, id = rand_id("tokenfilter") )
A recipe object. The step will be added to the sequence of operations for this recipe.
One or more selector functions to choose which variables are affected by the step. See
recipes::selections()for more details.
Not used by this step since no new variables are created.
A logical to indicate if the quantities for preprocessing have been estimated.
A character string of variable names that will be populated (eventually) by the
termsargument. This is
NULLuntil the step is trained by
An integer. Maximal number of times a word can appear before getting removed.
An integer. Minimum number of times a word can appear before getting removed.
A logical. Should max_times and min_times be interpreted as a percentage instead of count.
An integer. Will only keep the top max_tokens tokens after filtering done by max_times and min_times. Defaults to 100.
A function. This function should take a vector of characters, and return a logical vector of the same length. This function will be applied to each observation of the data set. Defaults to
NULL. All other arguments will be ignored if this argument is used.
The words that will be keep will be stored here once this preprocessing step has be trained by
A logical. Should the step be skipped when the recipe is baked by
recipes::bake.recipe()? While all operations are baked when
recipes::prep.recipe()is run, some operations may not be able to be conducted on new data (e.g. processing the outcome variable(s)). Care should be taken when using
skip = FALSE.
A character string that is unique to this step to identify it.
An updated version of
recipe with the new step added
to the sequence of existing steps (if any).
This step allow you to limit the tokens you are looking at by filtering on
their occurrence in the corpus. You are able to exclude tokens if they appear
too many times or too few times in the data. It can be specified as counts
min_times or as percentages by setting
TRUE. In addition one can filter to only use the top
max_tokens is set to
Inf then all the tokens will be used.
This will generally lead to very large data sets when then tokens are words
or trigrams. A good strategy is to start with a low token count and go up
according to how much RAM you want to use.
It is strongly advised to filter before using step_tf or step_tfidf to limit the number of variables created.
tidy() this step, a tibble with columns
(the selectors or variables selected) and
value (number of unique tokens).
step_tokenize() to turn characters into
Other Steps for Token Modification:
library(recipes) library(modeldata) data(tate_text) tate_rec <- recipe(~., data = tate_text) %>% step_tokenize(medium) %>% step_tokenfilter(medium) tate_obj <- tate_rec %>% prep() bake(tate_obj, new_data = NULL, medium) %>% slice(1:2) #> # A tibble: 2 × 1 #> medium #> <tknlist> #> 1 [8 tokens] #> 2 [3 tokens] bake(tate_obj, new_data = NULL) %>% slice(2) %>% pull(medium) #> <textrecipes_tokenlist> #>  [3 tokens] #> # Unique Tokens: 3 tidy(tate_rec, number = 2) #> # A tibble: 1 × 3 #> terms value id #> <chr> <int> <chr> #> 1 medium NA tokenfilter_IPQeM tidy(tate_obj, number = 2) #> # A tibble: 1 × 3 #> terms value id #> <chr> <int> <chr> #> 1 medium 952 tokenfilter_IPQeM