transform: Transform an Object, for Example a Data Frame
In robertzk/monadicbase: The R Base Package

Description Usage Arguments Details Value Warning Note Author(s) See Also Examples

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.

1	transform(`_data`, ...)

`_data`	The object to be transformed
`...`	Further arguments of the form `tag=value`

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.

The modified value of _data.

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.

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

Peter Dalgaard

within for a more flexible approach, subset, list, data.frame

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

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