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.
step_relevel( recipe, ..., role = NA, trained = FALSE, ref_level, objects = NULL, skip = FALSE, id = rand_id("relevel") ) # S3 method for step_relevel tidy(x, ...)
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 |
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 |
skip | A logical. Should the step be skipped when the
recipe is baked by |
id | A character string that is unique to this step to identify it. |
x | A |
An updated version of recipe
with the new step
added to the sequence of existing steps (if any).
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.
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)#> [1] "UNKNOWN" "anything" "halal" #> [4] "kosher" "mostly anything" "mostly halal" #> [7] "mostly kosher" "mostly other" "mostly vegan" #> [10] "mostly vegetarian" "other" "strictly anything" #> [13] "strictly halal" "strictly kosher" "strictly other" #> [16] "strictly vegan" "strictly vegetarian" "vegan" #> [19] "vegetarian"