diff --git a/man/xts.Rd b/man/xts.Rd index b1bfc14c..8e5cb6c5 100644 --- a/man/xts.Rd +++ b/man/xts.Rd @@ -1,5 +1,6 @@ \name{xts} \alias{xts} +\alias{.xts} \alias{is.xts} \title{ Create Or Test For An xts Time-Series Object } \description{ @@ -15,22 +16,44 @@ xts(x = NULL, tzone = Sys.getenv("TZ"), ...) +.xts(x = NULL, + index, + tclass = c("POSIXct", "POSIXt"), + tzone = Sys.getenv("TZ"), + check = TRUE, + unique = FALSE, + ...) + is.xts(x) } \arguments{ \item{x}{ an object containing the time series data } - \item{order.by}{ a corresponding vector of unique times/dates - must be -of a known time-based class. See details. } - \item{frequency}{ numeric indicating frequency of \code{order.by}. See details. } - \item{unique}{ should index be checked for unique time-stamps? } - \item{tzone}{ time zone of series. This is ignored for Date indices } - \item{\dots}{ additional attributes to be added. See details. } + \item{order.by}{ a corresponding vector of dates/times of a known time-based + class. See Details. } + \item{index}{ a corresponding \emph{numeric} vector specified as seconds + since the UNIX epoch (1970-01-01 00:00:00.000) } + \item{frequency}{ numeric indicating frequency of \code{order.by}. See Details. } + \item{unique}{ check the index for unique timestamps? } + \item{check}{ check that the index is ordered? } + \item{tclass}{ time class to use for the index. See code{\link{tclass}}. } + \item{tzone}{ time zone of the index (ignored indices without a time + component, e.g. Date, yearmon, yearqtr). See \code{\link{tzone}}. } + \item{\dots}{ additional attributes to be added. See Details. } } \details{ An \code{xts} object extends the S3 class \code{zoo} from the package of the same name. +The \code{xts()} constructor is the preferred way to create xts objects. It +performs several checks to ensure it returns a well-formed xts object. The +\code{.xts()} constructor is mainly for internal use. It is more efficient than +the regular \code{xts()} constructor because it doesn't perform as many +validity checks. Use it with caution. + +% TODO: add notes here about the differences between 'empty', 'zero-width', and +% 'zero-length' xts objects. + Similar to zoo objects, xts objects must have an ordered index. While zoo indexes cannot contain duplicate values, xts objects have optionally supported duplicate index elements since version 0.5-0. The \code{xts} class has one @@ -51,7 +74,7 @@ incorrect format, non-existent time due to daylight saving time, etc). Because of how non-finite numbers are represented, a missing timestamp will always be at the end of the index (except if it is \code{-Inf}, which will be first). -Another difference is that the object may now carry additional +Another difference from \pkg{zoo} is that xts object may carry additional attributes that may be desired in individual time-series handling. This includes the ability to augment the objects data with meta-data otherwise not cleanly attachable to a standard zoo object. @@ -68,7 +91,7 @@ the object in a manner required by the user. Many xts-specific methods have been written to better handle the unique aspects of xts. These include, \sQuote{"["}, merge, cbind, rbind, c, Ops, lag, diff, coredata, head and tail. Additionally -there are xts specific methods for converting amongst R's different +there are xts specific methods for converting to/from R's different time-series classes. Subsetting via "[" methods offers the ability to specify dates by @@ -86,8 +109,8 @@ Leading zeros are not necessary. See the examples for more detail. Users may also extend the \code{xts} class to new classes to allow for method overloading. -Additional benefits derive from the use of \code{as.xts} and -\code{reclass}, which allow for lossless two-way conversion +Additional benefits derive from the use of \code{\link{as.xts}} and +\code{\link{reclass}}, which allow for lossless two-way conversion between common R time-series classes and the \code{xts} object structure. See those functions for more detail. @@ -108,8 +131,8 @@ automagically handle \emph{all} data objects as one would handle a \code{zoo} object. } -\seealso{ \code{\link{as.xts}}, \code{\link{reclass}}, - \code{\link{xtsAttributes}} } +\seealso{ \code{\link{as.xts}}, \code{\link{index}}, \code{\link{tclass}}, + \code{\link{tformat}}, \code{\link{tzone}}, \code{\link{xtsAttributes}} } \examples{ data(sample_matrix) sample.xts <- as.xts(sample_matrix, descr='my new xts object')