recipes: step_relevel – R documentation

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step_relevel

Relevel factors to a desired level

Description

step_relevel creates a specification of a recipe step that will reorder the provided factor columns so that the level specified by ref_level is first. This is useful for contr.treatment contrasts which take the first level as the reference.

Usage

step_relevel(
  recipe,
  ...,
  role = NA,
  trained = FALSE,
  ref_level,
  objects = NULL,
  skip = FALSE,
  id = rand_id("relevel")
)

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

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 that will be affected by the step. These variables should be character or factor types. 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.
`ref_level`	A single character value that will be used to relevel the factor column(s) (if the level is present).
`objects`	A list of objects that contain the information on factor levels that will be determined 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_relevel` object.

Details

The selected variables are releveled to a level (given by ref_level). Placing the ref_level in the first position.

Note that if the original columns are character, they will be converted to factors by this step.

Value

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

Examples

library(modeldata)
data(okc)
rec <- recipe(~ diet + location, data = okc) %>%
  step_unknown(diet, new_level = "UNKNOWN") %>%
  step_relevel(diet, ref_level = "UNKNOWN") %>%
  prep()

data <- bake(rec, okc)
levels(data$diet)

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