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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/relevel.R
\name{step_relevel}
\alias{step_relevel}
\title{Relevel factors to a desired level}
\usage{
step_relevel(
recipe,
...,
role = NA,
trained = FALSE,
ref_level,
objects = NULL,
skip = FALSE,
id = rand_id("relevel")
)
}
\arguments{
\item{recipe}{A recipe object. The step will be added to the
sequence of operations for this recipe.}
\item{...}{One or more selector functions to choose variables
for this step. See \code{\link[=selections]{selections()}} for more details.}
\item{role}{Not used by this step since no new variables are
created.}
\item{trained}{A logical to indicate if the quantities for
preprocessing have been estimated.}
\item{ref_level}{A single character value that will be used to
relevel the factor column(s) (if the level is present).}
\item{objects}{A list of objects that contain the information
on factor levels that will be determined by \code{\link[=prep]{prep()}}.}
\item{skip}{A logical. Should the step be skipped when the
recipe is baked by \code{\link[=bake]{bake()}}? While all operations are baked
when \code{\link[=prep]{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 \code{skip = TRUE} as it may affect
the computations for subsequent operations.}
\item{id}{A character string that is unique to this step to identify it.}
}
\value{
An updated version of \code{recipe} with the new step added to the
sequence of any existing operations.
}
\description{
\code{step_relevel} creates a \emph{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.
}
\details{
The selected variables are releveled to a level
(given by \code{ref_level}). Placing the \code{ref_level} in the first
position.
Note that if the original columns are character, they will be
converted to factors by this step.
}
\section{Case weights}{
The underlying operation does not allow for case weights.
}
\examples{
\dontshow{if (rlang::is_installed("modeldata")) (if (getRversion() >= "3.4") withAutoprint else force)(\{ # examplesIf}
data(Sacramento, package = "modeldata")
rec <- recipe(~ city + zip, data = Sacramento) \%>\%
step_unknown(city, new_level = "UNKNOWN") \%>\%
step_relevel(city, ref_level = "UNKNOWN") \%>\%
prep()
data <- bake(rec, Sacramento)
levels(data$city)
\dontshow{\}) # examplesIf}
}
\seealso{
Other dummy variable and encoding steps:
\code{\link{step_bin2factor}()},
\code{\link{step_count}()},
\code{\link{step_date}()},
\code{\link{step_dummy_extract}()},
\code{\link{step_dummy_multi_choice}()},
\code{\link{step_dummy}()},
\code{\link{step_factor2string}()},
\code{\link{step_holiday}()},
\code{\link{step_indicate_na}()},
\code{\link{step_integer}()},
\code{\link{step_novel}()},
\code{\link{step_num2factor}()},
\code{\link{step_ordinalscore}()},
\code{\link{step_other}()},
\code{\link{step_regex}()},
\code{\link{step_string2factor}()},
\code{\link{step_time}()},
\code{\link{step_unknown}()},
\code{\link{step_unorder}()}
}
\concept{dummy variable and encoding steps}
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