title: Repeated-measures / within-subjects ANOVA in R
body: <p>I'm attempting to run a repeated-meaures ANOVA using R. I've gone through various examples on various websites, but they never seem to talk about the error that I'm encountering. I assume I'm misunderstanding something important.</p>
  
  <p>The ANOVA I'm trying to run is on some data from an experiment using human participants. It has one DV and three IVs. All of the levels of all of the IVs are run on all participants, making it a three-way repeated-measures / within-subjects ANOVA.</p>
  
  <p>The code I'm running in R is as follows:</p>
  
  <pre><code>aov.output = aov(DV~ IV1 * IV2 * IV3 + Error(PARTICIPANT_ID / (IV1 * IV2 * IV3)),
                   data=fulldata)
  </code></pre>
  
  <p>When I run this, I get the following warning:</p>
  
  <pre><code>Error() model is singular
  </code></pre>
  
  <p>Any ideas what I might be doing wrong?</p>