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.

Note

Prior to R 2.3.0, the first argument was named x, but this caused trouble if people wanted to create a variable of that name. Names starting with an underscore are syntactically invalid, so the current choice should be less problematic.

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

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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