title: Simulating an interaction effect in a lmer() model in R
body: <p>Is there an R package with a function that can:</p>
  
  <p>(1) simulate the different values of an interaction variable,
  (2) plot a graph that demonstrates the effect of the interaction on Y for different values of the terms in interaction, and
  (3) works well with the models fitted with the lmer() function of the lme4 package?</p>
  
  <p>I have looked in arm, ez, coefplot2, and fanovaGraph packages, but could not find what I was looking for.</p>