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% File src/library/base/man/as.Date.Rd
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% File src/library/base/man/as.Date.Rd
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% Part of the R package, https://www.R-project.org
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% Part of the R package, https://www.R-project.org
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% Copyright 1995-2015 R Core Team
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% Copyright 1995-2017 R Core Team
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% Distributed under GPL 2 or later
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% Distributed under GPL 2 or later
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\name{as.Date}
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\name{as.Date}
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\alias{format.Date}
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\alias{format.Date}
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\alias{as.character.Date}
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\alias{as.character.Date}
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  Functions to convert between character representations and objects of
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  Functions to convert between character representations and objects of
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  class \code{"Date"} representing calendar dates.
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  class \code{"Date"} representing calendar dates.
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}
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}
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\usage{
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\usage{
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as.Date(x, \dots)
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as.Date(x, \dots)
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\method{as.Date}{character}(x, format, \dots)
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\method{as.Date}{character}(x, format, tryFormats = c("\%Y-\%m-\%d", "\%Y/\%m/\%d"),
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        optional = FALSE, \dots)
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\method{as.Date}{numeric}(x, origin, \dots)
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\method{as.Date}{numeric}(x, origin, \dots)
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\method{as.Date}{POSIXct}(x, tz = "UTC", \dots)
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\method{as.Date}{POSIXct}(x, tz = "UTC", \dots)
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\method{format}{Date}(x, \dots)
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\method{format}{Date}(x, \dots)
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\method{as.character}{Date}(x, \dots)
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\method{as.character}{Date}(x, \dots)
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}
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}
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\arguments{
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\arguments{
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  \item{x}{An object to be converted.}
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  \item{x}{an object to be converted.}
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  \item{format}{A character string.  If not specified, it will try
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  \item{format}{\code{\link{character}} string.  If not specified, it will try
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    \code{"\%Y-\%m-\%d"} then \code{"\%Y/\%m/\%d"} on the first
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    \code{tryFormats} one by one on the first non-\code{NA} element, and
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    give an error if none works.  Otherwise, the processing is via
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    \code{\link{strptime}}.}
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    non-\code{NA} element, and give an error if neither works.
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  \item{tryFormats}{\code{\link{character}} vector of \code{format}
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    Otherwise, the processing is via \code{\link{strptime}}}
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    strings to try if \code{format} is not specified.}
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  \item{optional}{\code{\link{logical}} indicating to return \code{NA}
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    (instead of signalling an error) if the format guessing does not succeed.}
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  \item{origin}{a Date object, or something which can be coerced by
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  \item{origin}{a \code{Date} object, or something which can be coerced by
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    \code{as.Date(origin, \dots)} to such an object.}
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    \code{as.Date(origin, \dots)} to such an object.}
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  \item{tz}{a time zone name.}
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  \item{tz}{a time zone name.}
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  \item{\dots}{Further arguments to be passed from or to other methods,
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  \item{\dots}{further arguments to be passed from or to other methods,
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    including \code{format} for \code{as.character} and \code{as.Date}
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    including \code{format} for \code{as.character} and \code{as.Date}
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    methods.}
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    methods.}
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}
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}
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\details{
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\details{
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  The usual vector re-cycling rules are applied to \code{x} and
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  The usual vector re-cycling rules are applied to \code{x} and
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## Experiment shows that Matlab's origin is 719529 days before ours,
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## Experiment shows that Matlab's origin is 719529 days before ours,
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## (it takes the non-existent 0000-01-01 as day 1)
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## (it takes the non-existent 0000-01-01 as day 1)
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## so Matlab day 734373 can be imported as
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## so Matlab day 734373 can be imported as
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as.Date(734373, origin = "1970-01-01") - 719529 # 2010-08-23
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as.Date(734373, origin = "1970-01-01") - 719529 # 2010-08-23
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## (value from
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## (value from
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## http://www.mathworks.de/de/help/matlab/matlab_prog/represent-date-and-times-in-MATLAB.html)
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## http://www.mathworks.de/de/help/matlab/matlab_prog/represent-date-and-times-in-MATLAB.html)
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## Time zone effect
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## Time zone effect
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z <- ISOdate(2010, 04, 13, c(0,12)) # midnight and midday UTC
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z <- ISOdate(2010, 04, 13, c(0,12)) # midnight and midday UTC
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as.Date(z) # in UTC
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as.Date(z) # in UTC