[R] summarizing dataframe at variable/factor levels

D L McArthur dmca at ucla.edu
Thu Jul 5 18:45:34 CEST 2007

Afshartous, David <afshart <at> exchange.sba.miami.edu> writes:

> All,
> Is there an efficient way to apply say "mean" or "median" to a dataframe
> according to say all combinations of two variables in the dataframe?
> ..[snip]..
See function summaryBy in package doBy

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