recipes: step_regex – R documentation

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step_regex

Create Dummy Variables using Regular Expressions

Description

step_regex creates a specification of a recipe step that will create a new dummy variable based on a regular expression.

Usage

step_regex(
  recipe,
  ...,
  role = "predictor",
  trained = FALSE,
  pattern = ".",
  options = list(),
  result = make.names(pattern),
  input = NULL,
  skip = FALSE,
  id = rand_id("regex")
)

## S3 method for class 'step_regex'
tidy(x, ...)

Arguments

`recipe`	A recipe object. The step will be added to the sequence of operations for this recipe.
`...`	A single selector functions to choose which variable will be searched for the pattern. The selector should resolve into a single variable. See `selections()` for more details. For the `tidy` method, these are not currently used.
`role`	For a variable created by this step, what analysis role should they be assigned?. By default, the function assumes that the new dummy variable column created by the original variable will be used as a predictor in a model.
`trained`	A logical to indicate if the quantities for preprocessing have been estimated.
`pattern`	A character string containing a regular expression (or character string for `fixed = TRUE`) to be matched in the given character vector. Coerced by `as.character` to a character string if possible.
`options`	A list of options to `grepl()` that should not include `x` or `pattern`.
`result`	A single character value for the name of the new variable. It should be a valid column name.
`input`	A single character value for the name of the variable being searched. This is `NULL` until computed by `prep.recipe()`.
`skip`	A logical. Should the step be skipped when the recipe is baked by `bake.recipe()`? While all operations are baked when `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 = TRUE` as it may affect the computations for subsequent operations
`id`	A character string that is unique to this step to identify it.
`x`	A `step_regex` object.

Value

An updated version of recipe with the new step added to the sequence of existing steps (if any). For the tidy method, a tibble with columns terms (the selectors or variables selected) and result (the new column name).

Examples

library(modeldata)
data(covers)

rec <- recipe(~ description, covers) %>%
  step_regex(description, pattern = "(rock|stony)", result = "rocks") %>%
  step_regex(description, pattern = "ratake families")

rec2 <- prep(rec, training = covers)
rec2

with_dummies <- bake(rec2, new_data = covers)
with_dummies
tidy(rec, number = 1)
tidy(rec2, number = 1)

recipes

Preprocessing Tools to Create Design Matrices

v0.1.16

MIT + file LICENSE

Authors

Max Kuhn [aut, cre], Hadley Wickham [aut], RStudio [cph]

Initial release