equality constraints in lmer/lme4
If X1 and X2 are both numeric variables then Outcome ~ I( X1 + X2 ) + (1|Subject) should give you what you need. If both are categorical, then you need to create a set of variables that represent the combination (make sure that you understand what that combination represents). On Sun, Oct 20, 2013 at 7:52 PM, Jean-Philippe Laurenceau
<jlaurenceau at psych.udel.edu> wrote:
Dear R-sig-ME list--
When specifying the following lmer model, I get intercept fixed and random effects, a fixed effect for the X1 predictor, and a fixed effect for the X2 predictor.
fm <- lmer ( Outcome ~ X1 + X2 + ( 1 | Subject ), data = mydata)
My question: is there a way to ask lme4 to re-estimate this model but set an equality constraint on the effects of X1 and X2, such that their estimates would be equal to each other?
Thanks for your time, J-P
Jean-Philippe Laurenceau, Ph.D.
Department of Psychology
University of Delaware
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