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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

r
plyr
package
data
transformation
statistics
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

january 2012 by jerid.francom