% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/constant_check.R
\name{constant_check}
\alias{constant_check}
\title{Check Constant Variables}
\usage{
constant_check(data)
}
\arguments{
\item{data}{A data.frame.}
}
\value{
A data.frame of class \code{ConstantCheck}
containing the number of unique non-missing values,
missing values, and constant-variable status for each
variable.
}
\description{
Identifies variables that contain no meaningful
variation.
}
\details{
A variable is classified as constant when it contains
one or fewer unique non-missing values.

Missing values are excluded when counting unique values.
Consequently, a variable containing only missing values
is also classified as constant.
}
\examples{
dat <- data.frame(
  id = 1:5,
  group = rep("A", 5),
  value = c(10, 10, 10, NA, 10)
)

constant_check(dat)

}
