by-transform function

Function to make groupwise transformations

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

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

Returns

The modified value of the dataframe data.

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.

Examples

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

See Also

orderBy, order_by, summaryBy, summary_by, splitBy, split_by

Author(s)

Søren Højsgaard, sorenh@math.aau.dk