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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/classdist.R
\name{step_classdist}
\alias{step_classdist}
\title{Distances to Class Centroids}
\usage{
step_classdist(
recipe,
...,
class,
role = "predictor",
trained = FALSE,
mean_func = mean,
cov_func = cov,
pool = FALSE,
log = TRUE,
objects = NULL,
prefix = "classdist_",
skip = FALSE,
id = rand_id("classdist")
)
}
\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{class}{A single character string that specifies a single
categorical variable to be used as the class.}
\item{role}{For model terms created by this step, what analysis role should
they be assigned? By default, the new columns created by this step from
the original variables will be used as \emph{predictors} in a model.}
\item{trained}{A logical to indicate if the quantities for
preprocessing have been estimated.}
\item{mean_func}{A function to compute the center of the
distribution.}
\item{cov_func}{A function that computes the covariance matrix}
\item{pool}{A logical: should the covariance matrix be computed
by pooling the data for all of the classes?}
\item{log}{A logical: should the distances be transformed by
the natural log function?}
\item{objects}{Statistics are stored here once this step has
been trained by \code{\link[=prep]{prep()}}.}
\item{prefix}{A character string for the prefix of the resulting new
variables. See notes below.}
\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_classdist} creates a \emph{specification} of a
recipe step that will convert numeric data into Mahalanobis
distance measurements to the data centroid. This is done for
each value of a categorical class variable.
}
\details{
\code{step_classdist} will create a new column for every
unique value of the \code{class} variable.
The resulting variables will not replace the original values
and by default have the prefix \code{classdist_}. The naming format can be
changed using the \code{prefix} argument.
Note that, by default, the default covariance function requires
that each class should have at least as many rows as variables
listed in the \code{terms} argument. If \code{pool = TRUE},
there must be at least as many data points are variables
overall.
}
\section{Tidying}{
When you \code{\link[=tidy.recipe]{tidy()}} this step, a tibble with columns
\code{terms} (the selectors or variables selected), \code{value} (the centroid
of the class), and \code{class} is returned.
}
\section{Case weights}{
This step performs an supervised operation that can utilize case weights.
As a result, case weights are used with frequency weights as well as
importance weights. For more information,, see the documentation in
\link{case_weights} and the examples on \code{tidymodels.org}.
}
\examples{
# in case of missing data...
mean2 <- function(x) mean(x, na.rm = TRUE)
# define naming convention
rec <- recipe(Species ~ ., data = iris) \%>\%
step_classdist(all_numeric_predictors(),
class = "Species",
pool = FALSE, mean_func = mean2, prefix = "centroid_"
)
# default naming
rec <- recipe(Species ~ ., data = iris) \%>\%
step_classdist(all_numeric_predictors(),
class = "Species",
pool = FALSE, mean_func = mean2
)
rec_dists <- prep(rec, training = iris)
dists_to_species <- bake(rec_dists, new_data = iris, everything())
## on log scale:
dist_cols <- grep("classdist", names(dists_to_species), value = TRUE)
dists_to_species[, c("Species", dist_cols)]
tidy(rec, number = 1)
tidy(rec_dists, number = 1)
}
\seealso{
Other multivariate transformation steps:
\code{\link{step_depth}()},
\code{\link{step_geodist}()},
\code{\link{step_ica}()},
\code{\link{step_isomap}()},
\code{\link{step_kpca_poly}()},
\code{\link{step_kpca_rbf}()},
\code{\link{step_kpca}()},
\code{\link{step_mutate_at}()},
\code{\link{step_nnmf_sparse}()},
\code{\link{step_nnmf}()},
\code{\link{step_pca}()},
\code{\link{step_pls}()},
\code{\link{step_ratio}()},
\code{\link{step_spatialsign}()}
}
\concept{multivariate transformation steps}
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