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\name{date.object}
\alias{is.date}
\alias{Math.date}
\alias{Ops.date}
\alias{Summary.date}
\alias{[.date}
\alias{[[.date}
\alias{as.character.date}
\alias{as.data.frame.date}
\alias{as.vector.date}
\alias{is.na.date}
\alias{plot.date}
\alias{print.date}
\alias{summary.date}
\title{Date Objects}
\description{
Objects of class \code{"date"}.
}
\usage{
is.date(x)
}
\arguments{
\item{x}{any R object.}
}
\details{
Dates are stored as the number of days since 1/1/1960, and are kept
in integer format. (This is the same baseline value as is used by
SAS). The numerical methods for dates treat \code{date - date} as a
numeric, and \code{date +- numeric} as a date.
\code{is.date} returns \code{TRUE} if \code{x} has class
\code{"date"}, and \code{FALSE} otherwise. Its behavior is unaffected
by any attributes of \code{x}; for example, \code{x} could be a date
array (in contrast to the behavior of \code{is.vector}).
\code{as.date} returns \code{x} if \code{x} is a simple object of
class \code{"date"}, and otherwise a date vector of the same length as
\code{x} and with data resulting from coercing the elements of
\code{x} to class \code{"date"}. See the manual page for
\code{as.date()} for details.
Logical operations as well as the numeric functions \code{exp()},
\code{log()}, and so on are invalid.
Other methods exist for missing value, \code{as.character()},
printing, and summarizing.
}
\seealso{
\code{\link{date.mdy}},
\code{\link{mdy.date}},
\code{\link{date.ddmmmyy}},
\code{\link{as.date}}.
}
\keyword{chron}
|
