[R] using tapply with a matrix?

[Nurnberg-LaZerte]

** Reply to message from Thomas Lumley <tlumley at u.washington.edu> on Mon, 24 Mar 2003 14:30:44 -0800 (PST)

>Use by()

That's what I need. 

Somebody should put a link to by() in the tapply() section of the html docs.

Thanks.