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\name{sort}
\alias{sort}
\alias{sort.timeSeries}
\alias{is.unsorted}
\alias{is.unsorted.timeSeries}
\alias{is.unsorted,timeSeries-method}
\title{Sort a 'timeSeries' by time stamps}
\description{
Sort a \code{"timeSeries"} object with respect to its time stamps.
}
\usage{
\method{sort}{timeSeries}(x, decreasing = FALSE, \dots)
\S4method{is.unsorted}{timeSeries}(x, na.rm = FALSE, strictly = FALSE)
}
\arguments{
\item{x}{
a \code{"timeSeries"} object.
}
\item{decreasing}{
a logical flag. Should we sort in increasing or decreasing order?
By default \code{FALSE}.
}
\item{na.rm}{
a logical value, should missing values be removed?
}
\item{strictly}{
logical indicating if the check should be for strictly increasing
values.
}
\item{\dots}{
optional arguments passed to other methods.
}
}
\details{
The method for \code{sort} sorts \code{x} either in increasing or
decreasing time stamp order.
The method for \code{is.unsorted} returns \code{TRUE} if the time
stamps of \code{x} are not sorted in increasing order (including the
case when they are sorted in decreasing order) and \code{FALSE}
otherwise. \code{is.unsorted} may also return \code{NA} when there are
\code{NA}s among the time stamps of \code{x}.
All this is in line with the documented functionality of
\code{base::is.unsorted}.
}
\value{
for \code{sort}, a \code{"timeSeries"} object,
for the \code{is.unsorted} method, \code{TRUE}, \code{FALSE}, or
\code{NA}, as described in section \sQuote{Details}.
}
\note{
If \code{is.unsorted} returns \code{NA} when there are \code{NA}s in
the data but not in the time stamps use \code{library{timeSeries}} or
call the function as \code{timeSeries::is.unsorted}. If you need more
details, read the rest of this note.
\code{base::is.unsorted} 'sees' the method for \code{"timeSeries"}
objects when package timeSeries is loaded (whether or not it is
attached). However, due to the way \code{base::is.unsorted} is
implemented, it may give wrong answers when there are \code{NA}'s
among the values of the time series. Developers of packages applying
\code{is.unsorted} on timeSeries objects should import if from package
timeSeries.
The above feature is not a shortcoming of \code{base::is.unsorted} but
a consequence of the fact that the timeSeries method is not consistent
with its semantics. For example, it works on the time stamps, while
\code{is.na} works on the data values.
}
\seealso{
\code{\link[base]{is.unsorted}} for further details on the \code{NA} case
}
\examples{
## a monthly calendar series
x <- daily2monthly(LPP2005REC[, 1:2])[3:14, ]
\dontshow{set.seed(1234)}
## resample the series with respect to the time stamps,
resampled <- sample(x)
## the time stamps are unordered
resampled
is.unsorted(resampled) # TRUE (i.e., not sorted)
## Now sort the series in decreasing time order
backward_in_time <- sort(resampled, , decreasing = TRUE)
## time stamps ordered in decreasing order
## but is.unordered requires increasing order:
backward_in_time
is.unsorted(backward_in_time) # still TRUE
## Is the reverted series ordered?
forward_in_time <- rev(backward_in_time)
forward_in_time
is.unsorted(forward_in_time) # FALSE (i.e., sorted)
}
\keyword{chron}
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