step_factor2string: Convert factors to strings

In topepo/recipes: Preprocessing and Feature Engineering Steps for Modeling

Convert factors to strings

Description

step_factor2string() creates a specification of a recipe step that will convert one or more factor vectors to strings.

Usage

step_factor2string(
  recipe,
  ...,
  role = NA,
  trained = FALSE,
  columns = FALSE,
  skip = FALSE,
  id = rand_id("factor2string")
)

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 variables for this step. See 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 the selected variable names. This field is a placeholder and will be populated once prep() is used.
skip	A logical. Should the step be skipped when the recipe is baked by bake()? While all operations are baked when prep() 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 = TRUE as it may affect the computations for subsequent operations.
id	A character string that is unique to this step to identify it.

Details

prep() has an option strings_as_factors that defaults to TRUE. If this step is used with the default option, the strings produced by this step will not be converted to factors.

Remember that categorical data that will be directly passed to a model should be encoded as factors. This step is helpful for ancillary columns (such as identifiers) that will not be computed on in the model.

Value

An updated version of recipe with the new step added to the sequence of any existing operations.

Tidying

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

terms

character, the selectors or variables selected

id

character, id of this step

Case weights

The underlying operation does not allow for case weights.

See Also

Other dummy variable and encoding steps: step_bin2factor(), step_count(), step_date(), step_dummy(), step_dummy_extract(), step_dummy_multi_choice(), step_holiday(), step_indicate_na(), step_integer(), step_novel(), step_num2factor(), step_ordinalscore(), step_other(), step_regex(), step_relevel(), step_string2factor(), step_time(), step_unknown(), step_unorder()

Examples

data(Sacramento, package = "modeldata")

rec <- recipe(~ city + zip, data = Sacramento)

make_string <- rec %>%
  step_factor2string(city)

make_string <- prep(make_string,
  training = Sacramento,
  strings_as_factors = FALSE
)

make_string

# note that `city` is a string in recipe output
bake(make_string, new_data = NULL) %>% head()

# ...but remains a factor in the original data
Sacramento %>% head()

topepo/recipes documentation built on April 10, 2024, 10:30 p.m.