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Rev 72237 Rev 73898
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  possibly modifying (a copy of) the original data.
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  possibly modifying (a copy of) the original data.
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}
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}
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\usage{
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\usage{
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with(data, expr, \dots)
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with(data, expr, \dots)
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within(data, expr, \dots)
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within(data, expr, \dots)
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\S3method{within}{list}(data, expr, keepAttrs = TRUE, \dots)
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}
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}
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\arguments{
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\arguments{
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  \item{data}{data to use for constructing an environment. For the
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  \item{data}{data to use for constructing an environment. For the
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    default \code{with} method this may be an environment, a list, a
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    default \code{with} method this may be an environment, a list, a
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    data frame, or an integer as in \code{sys.call}. For \code{within},
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    data frame, or an integer as in \code{sys.call}. For \code{within},
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    it can be a list or a data frame.}
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    it can be a list or a data frame.}
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  \item{expr}{expression to evaluate.}
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  \item{expr}{expression to evaluate; particularly for \code{within()}
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    often a \dQuote{compound} expression, i.e., of the form \preformatted{   {
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     a <- somefun()
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     b <- otherfun()
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     .....
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     rm(unused1, temp)
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   }
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}}
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  \item{keepAttrs}{for the \code{\link{list}} method of \code{within()},
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    a \code{\link{logical}} specifying if the resulting list should keep
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    the \code{\link{attributes}} from \code{data} and have its
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    \code{\link{names}} in the same order.  Often this is unneeded as
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    the result is a \emph{named} list anyway, and then \code{keepAttrs =
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      FALSE} is more efficient.}
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  \item{\dots}{arguments to be passed to future methods.}
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  \item{\dots}{arguments to be passed to (future) methods.}
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}
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}
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\details{
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\details{
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  \code{with} is a generic function that evaluates \code{expr} in a
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  \code{with} is a generic function that evaluates \code{expr} in a
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  local environment constructed from \code{data}.  The environment has
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  local environment constructed from \code{data}.  The environment has
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  the caller's environment as its parent.  This is useful for
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  the caller's environment as its parent.  This is useful for
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    S.cT <- Solar.R / cTemp  # using the newly created variable
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    S.cT <- Solar.R / cTemp  # using the newly created variable
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    rm(Day, Temp)
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    rm(Day, Temp)
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})
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})
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head(aq)
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head(aq)
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# example from boxplot:
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# example from boxplot:
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with(ToothGrowth, {
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with(ToothGrowth, {
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    boxplot(len ~ dose, boxwex = 0.25, at = 1:3 - 0.2,
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    boxplot(len ~ dose, boxwex = 0.25, at = 1:3 - 0.2,
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            subset = (supp == "VC"), col = "yellow",
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            subset = (supp == "VC"), col = "yellow",
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            main = "Guinea Pigs' Tooth Growth",
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            main = "Guinea Pigs' Tooth Growth",