[R] tapply

Manuel Montes jmmontes at uni-hohenheim.de
Tue Apr 8 11:14:13 CEST 2008

Does anyone have something like tapply for matrices? I would like to average the contents of columns 
according to factors but tapply works only with one column at each time. Is something available to do 
everything in one step?
Many thanks.
Manuel Montes

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