[R] contrast/test statements in polynomial mixed model

Dede Greenstein dede01 at codon.nih.gov
Tue Sep 7 19:05:32 CEST 2004


I am having some trouble figuring out how to write contrast/test syntax for 
the following mixed model regression  y ~ group*age  + group*age^2 random 

(i have centered the age variable & there are only 2 groups)

the contrast i am trying to construct should compare the overall shape of 
the 2 groups -- in SAS,  this does the trick  -- test 'group difference in 
shape' age_squared*group1 -1; age_cent*group 1 -1

Suggestions would be greatly appreciated

Thanks in advance

Dede Greenstein

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