title: Missing Outputs from Three-Way ANOVA
body: <p>I am trying to do a 3-way ANOVA using this code:</p>
  <pre><code>ANOVA &lt;- aov(df$GSI ~ df$Area * df$Site * df$Gear, data = df)
  summary(ANOVA)
  </code></pre>
  <p>But the summary output only gives me these rows:</p>
  <pre><code>df$Area
  df$Site
  df$Gear
  df$Area:df$Gear
  df$Site:df$Gear
  Residuals
  </code></pre>
  <p>It is missing the rows for <code>df$Area:df$Site</code> and <code>df$Area:df$Site:df$Gear</code>. I have also tried writing out the code like this:</p>
  <pre><code>ANOVA &lt;- aov(df$GSI ~ df$Area + df$Site + df$Gear + 
             df$Area:df$Site + df$Area:df$Gear + df$Site:df$Gear +
             df$Area:df$Site:df$Gear, data = df)
  </code></pre>
  <p>And it gives me the same result. Why are some results missing from my ANOVA summary?</p>