From: David J. Netherway (firstname.lastname@example.org)
Date: Mon 03 May 2004 - 18:25:12 EST
I am using the following model:
lm <- lm(mydata[[variableName]] ~ Age + Gender + Group, data=mydata)
There are 5 groups in "Group": nonc (the control), c1,c2,c3 and c4.
How do I contrast nonc vs the others?
How do I contrast c1 vs other c's (ie c2,c3,c4 as a subgroup)?
I have looked at the contrasts option in lm and model.matrix and am
really none the wiser.
Though it looks like I need to read up on model matrices again.
Any help would be appreciated.
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