plyr

plyr is a set of tools for a common set of problems: you need to split up a big data structure into homogeneous pieces, apply a function to each piece and then combine all the results back together. For example, you might want to: fit the same model to subsets of a data frame quickly calculate summary statistics for each group perform group-wise transformations like scaling or standardising It’s a

[koemu]

データの前処理を便利に行ってくれるライブラリ群

[sessan]

Rでdata.frameを扱うときにすごく便利そうなライブラリ。plyr。