Aloha all,

I have a data frame with 4 columns.  The first three are factors (f1,  
f2, f3) and the fourth is numeric.  I'd like to explore these data  
using median polish.  To do that I plan to use medpolish() on the  
matrix[f1,f2xf3], then medpolish on the resulting matrix[f2,f3].  This  
approach is described by Cook on page 141 of Exploring Data Tables,  
Trends, and Shapes.

split() gets me close to where I want to be, but results in a list,  
rather than a matrix.  How do I construct the matrix[f1,f2xf3] from my  
data frame?

Also, any pointers to existing code that performs multi-way median  
polish will be appreciated.

Sorry for the newbie-type query, but manipulating data prior to  
analysis is really hard for me in R.

All the best,
Tom

Thomas S. Dye, Ph.D.
T. S. Dye & Colleagues, Archaeologists, Inc.
Phone: (808) 529-0866 Fax: (808) 529-0884
http://www.tsdye.com



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