R: Function to make groupwise transformations

by-transform {doBy} | R Documentation

## Function to make groupwise transformations

### Description

Function to make groupwise transformations of data by applying the transform function to subsets of data.

### Usage

    transform_by(data, formula, ...)

    transformBy(formula, data, ...)

### Arguments

`data` | A data frame
`formula` | A formula with only a right hand side, see examples below
`...` | Further arguments of the form tag=value

### Details

The ... arguments 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 the dataframe data.

### Author(s)

Søren Højsgaard, sorenh@math.aau.dk

### See Also

`orderBy`, `summaryBy`, `splitBy`

### Examples

    data(dietox)
    transformBy(~Pig, data=dietox, minW=min(Weight), maxW=max(Weight),
        gain=diff(range(Weight)))

[Package doBy version 4.6.6 Index]