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\usage{
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\usage{
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subset(x, \dots)
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subset(x, \dots)
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\method{subset}{default}(x, subset, \dots)
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\method{subset}{default}(x, subset, \dots)
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\method{subset}{data.frame}(x, subset, select, \dots)
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\method{subset}{data.frame}(x, subset, select, drop = FALSE, \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}{object to be subsetted.}
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  \item{x}{object to be subsetted.}
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  \item{subset}{logical expression.}
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  \item{subset}{logical expression.}
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  \item{select}{expression, indicating columns to select from a
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  \item{select}{expression, indicating columns to select from a
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    data frame.}
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    data frame.}
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  \item{drop}{passed on to \code{[} indexing operator.}
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  \item{\dots}{further arguments to be passed to or from other methods.}
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  \item{\dots}{further arguments to be passed to or from other methods.}
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}
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}
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\details{
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\details{
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  For ordinary vectors, the result is simply
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  For ordinary vectors, the result is simply
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  \code{x[subset & !is.na(subset)]}.
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  \code{x[subset & !is.na(subset)]}.
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  first replacing names in the selection expression with the
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  first replacing names in the selection expression with the
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  corresponding column numbers in the data frame and then using the
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  corresponding column numbers in the data frame and then using the
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  resulting integer vector to index the columns.  This allows the use
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  resulting integer vector to index the columns.  This allows the use
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  of the standard indexing conventions so that for example ranges of
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  of the standard indexing conventions so that for example ranges of
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  columns can be specified easily.
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  columns can be specified easily.
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  Setting \code{drop=TRUE} will drop unused levels from factors in a
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  data frame. The default is to retain them.
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}
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}
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\value{
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\value{
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  An object similar to \code{x} contain just the selected elements (for
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  An object similar to \code{x} contain just the selected elements (for
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  a vector), rows and columns (for a data frame), and so on.
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  a vector), rows and columns (for a data frame), and so on.
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}
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}