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(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 data frame `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)

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