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% File src/library/base/man/system.time.Rd
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% File src/library/base/man/system.time.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 1995-2011 R Core Team
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% Copyright 1995-2016 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{system.time}
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\name{system.time}
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\title{CPU Time Used}
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\title{CPU Time Used}
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\usage{
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\usage{
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system.time(expr, gcFirst = TRUE)
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system.time(expr, gcFirst = TRUE)
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unix.time(expr, gcFirst = TRUE)
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%Deprecated unix.time(expr, gcFirst = TRUE)
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}
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}
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\alias{system.time}
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\alias{system.time}
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\alias{unix.time}
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\alias{unix.time}
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\arguments{
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\arguments{
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  \item{expr}{Valid \R expression to be timed.}
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  \item{expr}{Valid \R expression to be timed.}
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\details{
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\details{
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  \code{system.time} calls the function \code{\link{proc.time}},
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  \code{system.time} calls the function \code{\link{proc.time}},
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  evaluates \code{expr}, and then calls \code{proc.time} once more,
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  evaluates \code{expr}, and then calls \code{proc.time} once more,
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  returning the difference between the two \code{proc.time} calls.
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  returning the difference between the two \code{proc.time} calls.
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  \code{unix.time} is an alias of \code{system.time}, for
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  \code{unix.time} has been an alias of \code{system.time}, for
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  compatibility with S.
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  compatibility with S, and has finally been deprecated in 2016.
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  Timings of evaluations of the same expression can vary considerably
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  Timings of evaluations of the same expression can vary considerably
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  depending on whether the evaluation triggers a garbage collection.  When
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  depending on whether the evaluation triggers a garbage collection.  When
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  \code{gcFirst} is \code{TRUE} a garbage collection (\code{\link{gc}})
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  \code{gcFirst} is \code{TRUE} a garbage collection (\code{\link{gc}})
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  will be performed immediately before the evaluation of \code{expr}.
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  will be performed immediately before the evaluation of \code{expr}.
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  A object of class \code{"proc_time"}: see
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  A object of class \code{"proc_time"}: see
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  \code{\link{proc.time}} for details.
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  \code{\link{proc.time}} for details.
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}
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}
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\seealso{
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\seealso{
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  \code{\link{proc.time}}, \code{\link{time}} which is for time series.
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  \code{\link{proc.time}}, \code{\link{time}} which is for time series.
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  \code{\link{Sys.time}} to get the current date & time.
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  \code{\link{Sys.time}} to get the current date & time.
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}
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}
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\examples{
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\examples{
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require(stats)
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require(stats)
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\donttest{system.time(for(i in 1:100) mad(runif(1000)))}
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\donttest{system.time(for(i in 1:100) mad(runif(1000)))}