Hello Everyone,
 
Figured out one part of the code. Setting the reference level for a factor is accomplished using the relevel funtion (pg. 383 of MASS; pg. 70 of Data Manipulation with R):
 
gad$dosegrp <- relevel(gad$dosegrp,3)
 
This works very well. Much better than using a format in SAS procedures that don't allow the "ref=" option for instance.
 
Does anyone have suggestions about how to improve other aspects of my code?
 
Thanks,
 
Paul
 


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