transform                package:base                R Documentation

Transform an Object, e.g. a Data Frame

Description:

     `transform' is a generic function, which-at least currently-only
     does anything useful with dataframes. `transform.default' converts
     its first argument to a dataframe if possible and calls
     `transform.data.frame'.

Usage:

     transform(x, ...)
     transform.default(x, ...)
     transform.data.frame(x, ...)

Arguments:

       x: The object to be transformed

     ...: Further arguments of the form `tag=value'

Details:

     The `...' arguments to `transform.data.frame' are tagged vector
     expressions, which are evaluated in the dataframe `x'.  The tags
     are matched against `names(x)', and for those that match, the
     value replace the corresponding variable in `x', and the others
     are appended to `x'.

Value:

     The modified value of `x'.

Note:

     If some of the values are not vectors of the appropriate length,
     you deserve whatever you get!

Author(s):

     Peter Dalgaard

See Also:

     `subset', `list', `data.frame'

Examples:

     data(airquality)
     transform(airquality, Ozone = -Ozone)
     transform(airquality, new = -Ozone, Temp = (Temp-32)/1.8)

     attach(airquality)
     transform(Ozone, logOzone = log(Ozone)) # marginally interesting ...
     detach(airquality)

