transform
Transform an Object, for Example a Data Frame
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.
- Keywords
- manip
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
If some of the values are not vectors of the appropriate length, you deserve whatever you get!
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.
See Also
within for a more flexible approach,
subset,
list,
data.frame
Examples
library(base)
transform(airquality, Ozone = -Ozone)
transform(airquality, new = -Ozone, Temp = (Temp-32)/1.8)
attach(airquality)
transform(Ozone, logOzone = log(Ozone)) # marginally interesting ...
detach(airquality)
Community examples
mtcars <- transform(mtcars, mpg=mpg^2)