The R Project SVN R

\name{subset}
\title{Subsetting vectors and data frames}
\usage{
subset(x, ...)
}
\usage{
subset.default(x, subset)
}
\usage{
subset.data.frame(x, subset, select)
}
%- maybe also `usage' for other functions documented here.
\alias{subset}
\alias{subset.default}
\alias{subset.data.frame}
\arguments{
 \item{x}{Object to be subsetted}
 \item{\dots}{How to subset, depends on object}
 \item{subset}{logical expression}
 \item{select}{expression, indicating variables to select from a dataframe}
}
\description{
For ordinary vectors, the result is simply 

\code{x[subset&!is.na(subset)]}. 

For dataframes, the \code{subset} argument works similarly on the rows. 
Note that \code{subset} will be evaluated in the dataframe.

The  \code{select} argument exists only for dataframes. It works by 
first replacing variable names in the selection expression with the 
corresponding column numbers in the dataframe and then using the 
resulting integer vector to index the columns. This allows the use 
of the standard indexing conventions so that e.g. ranges of variables
can be specified easily.
}

\value{
   Selected rows and columns of the object \code{x}
}
\author{Peter Dalgaard}
\seealso{\code{\link{"["}}, \code{\link{transform}}}

\examples{
data(airquality)
subset(airquality,Temp>80,select=c(Ozone,Temp))
subset(airquality,Day==1,select=-Temp)
subset(airquality,select=Ozone:Wind)

attach(airquality)
subset(Ozone,Temp>80)
}
\keyword{dataframes subset extract}