transform {base}R Documentation

Transform an Object, for Example a Data Frame

Description

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

Usage

transform(`_data`, ...)

Arguments

_data

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 data frame _data. The tags are matched against names(_data), and for those that match, the value replace the corresponding variable in _data, and the others are appended to _data.

Value

The modified value of _data.

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 transform can have unanticipated consequences.

Note

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

Author(s)

Peter Dalgaard

See Also

within for a more flexible approach, subset, list, 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)

[Package base version 3.1.0 Index]