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\name{isRegular}
\alias{isRegular}
\alias{isRegular,timeSeries-method}
\alias{isRegular.timeSeries}
\alias{isDaily}
\alias{isDaily,timeSeries-method}
\alias{isDaily.timeSeries}
\alias{isMonthly}
\alias{isMonthly,timeSeries-method}
\alias{isMonthly.timeSeries}
\alias{isQuarterly}
\alias{isQuarterly,timeSeries-method}
\alias{isQuarterly.timeSeries}
\alias{frequency}
\alias{frequency,timeSeries-method}
\alias{frequency.timeSeries}
\title{Checks if a time series is regular}
\description{
Checks if a time series is regular.
}
\usage{
\S4method{isDaily}{timeSeries}(x)
\S4method{isMonthly}{timeSeries}(x)
\S4method{isQuarterly}{timeSeries}(x)
\S4method{isRegular}{timeSeries}(x)
\S4method{frequency}{timeSeries}(x, \dots)
}
\arguments{
\item{x}{
an R object of class 'timeSeries'.
}
\item{\dots}{
arguments to be passed.
}
}
\details{
What is a regular time series? If a time series is daily, monthly, or
weekly, then we speak of a regular series. This can be tested calling
the functions \code{isDaily}, \code{isMonthly}, \code{isQuarterly}, or
in general \code{isRegular}. If the series is regular then its
frequency can be determined by calling \code{frequency}.
Here are the definitions of daily, monthly, and quarterly time series:
\describe{
\item{daily}{if the series has no more than one date/time stamp per
day.}
\item{monthly}{if the series has no more than one date/time stamp
per month.}
\item{quarterly}{if the series has no more than one date/time stamp
per quarter.}
}
A regular series is either a monthly or a quarterly series.
Note that with the above definitions a monthly series is also a daily
series, a quarterly series is also a monthly series. On the other
hand, a daily series is not regular!
NOT yet implemented is the case of weekly series.
}
\value{
The \code{is*} functions return \code{TRUE} or \code{FALSE} depending
on whether the series fulfills the condition or not.\cr
\code{frequency} returns in general 1, for quarterly series 4,
and for monthly series 12.
}
\seealso{
\code{\link[timeDate]{isRegular}}
\code{\link[stats]{frequency}}
}
\examples{
data(MSFT)
isRegular(MSFT) # FALSE
frequency(MSFT) # 1
## a monthly ts
ap <- as.timeSeries(AirPassengers)
isRegular(ap) # TRUE
frequency(ap) # 12
## a quarterly ts
pres <- as.timeSeries(presidents)
isRegular(pres) # TRUE
frequency(pres) # 4
}
\keyword{chron}
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