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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