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Normalization of Character Variables

Source: R/text_normalization.R
step_text_normalization.Rd

step_text_normalization() creates a specification of a recipe step that will perform Unicode Normalization on character variables.

Usage

step_text_normalization(
  recipe,
  ...,
  role = NA,
  trained = FALSE,
  columns = NULL,
  normalization_form = "nfc",
  skip = FALSE,
  id = rand_id("text_normalization")
)

Arguments

recipe

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.

role

Not used by this step since no new variables are created.

trained

A logical to indicate if the quantities for preprocessing have been estimated.

columns

A character string of variable names that will be populated (eventually) by the terms argument. This is NULL until the step is trained by recipes::prep.recipe().

normalization_form

A single character string determining the Unicode Normalization. Must be one of "nfc", "nfd", "nfkd", "nfkc", or "nfkc_casefold". Defaults to "nfc". See stringi::stri_trans_nfc() for more details.

skip

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.

id

A character string that is unique to this step to identify it.

Value

An updated version of recipe with the new step added to the sequence of existing steps (if any).

Tidying

When you tidy() this step, a tibble is returned with columns terms, normalization_form, and id:

terms

character, the selectors or variables selected

normalization_form

character, type of normalization

id

character, id of this step

Case weights

The underlying operation does not allow for case weights.

See also

step_texthash() for feature hashing.

Examples

library(recipes)

sample_data <- tibble(text = c("sch\U00f6n", "scho\U0308n"))

rec <- recipe(~., data = sample_data) %>%
  step_text_normalization(text)

prepped <- rec %>%
  prep()

bake(prepped, new_data = NULL, text) %>%
  slice(1:2)
#> # A tibble: 2 × 1
#>   text 
#>   <fct>
#> 1 schön
#> 2 schön

bake(prepped, new_data = NULL) %>%
  slice(2) %>%
  pull(text)
#> [1] schön
#> Levels: schön

tidy(rec, number = 1)
#> # A tibble: 1 × 3
#>   terms normalization_form id                      
#>   <chr> <chr>              <chr>                   
#> 1 text  NA                 text_normalization_BfGx4
tidy(prepped, number = 1)
#> # A tibble: 1 × 3
#>   terms normalization_form id                      
#>   <chr> <chr>              <chr>                   
#> 1 text  nfc                text_normalization_BfGx4