R: Transform an Object, for Example a Data Frame

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 3.1.2 Index]