| % File src/library/base/man/transform.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2013 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{transform} |
| \alias{transform} |
| \alias{transform.default} |
| \alias{transform.data.frame} |
| \title{Transform an Object, for Example a Data Frame} |
| \usage{ |
| transform(`_data`, \dots) |
| } |
| \arguments{ |
| \item{_data}{The object to be transformed} |
| \item{\dots}{Further arguments of the form \code{tag=value}} |
| } |
| \description{ |
| \code{transform} is a generic function, which---at least |
| currently---only does anything useful with |
| data frames. \code{transform.default} converts its first argument to |
| a data frame if possible and calls \code{transform.data.frame}. |
| } |
| \details{ |
| The \code{\dots} arguments to \code{transform.data.frame} are tagged |
| vector expressions, which are evaluated in the data frame |
| \code{_data}. The tags are matched against \code{names(_data)}, and for |
| those that match, the value replace the corresponding variable in |
| \code{_data}, and the others are appended to \code{_data}. |
| } |
| \value{ |
| The modified value of \code{_data}. |
| } |
| \section{Warning}{ |
| This is a convenience function intended for use interactively. For |
| programming it is better to use the standard subsetting arithmetic functions, |
| and in particular the non-standard evaluation of |
| argument \code{transform} can have unanticipated consequences. |
| |
| } |
| \author{Peter Dalgaard} |
| \note{ |
| If some of the values are not vectors of the appropriate length, |
| you deserve whatever you get! |
| } |
| \seealso{ \code{\link{within}} for a more flexible approach, |
| \code{\link{subset}}, |
| \code{\link{list}}, |
| \code{\link{data.frame}} |
| } |
| \examples{ |
| transform(airquality, Ozone = -Ozone) |
| transform(airquality, new = -Ozone, Temp = (Temp-32)/1.8) |
| |
| attach(airquality) |
| transform(Ozone, logOzone = log(Ozone)) # marginally interesting ... |
| detach(airquality) |
| } |
| \keyword{manip} |