title: Fixed effects with ggeffect()
body: <p>I'm wondering if anyone has any experience using <code>ggeffect()</code> with lots of fixed effects. Although my independent variable is strongly related to my dependent variable, I get these massive confidence intervals when I add in state fixed effects.</p>
  
  <p>A toy example:</p>
  
  <pre><code>set.seed(200)
  
  indvar &lt;- runif(500, min = 0, max = .5)
  state &lt;- as.factor(rep(c(1:50), 10))
  statev &lt;- as.integer(state) * runif(500, 0, 0.02)
  depvar &lt;- round(indvar + statev)
  
  data &lt;- data.frame(indvar, state, depvar)
  
  m1 &lt;- glm(depvar ~ indvar, data = data, family = "binomial")
  
  margin &lt;- ggeffect(m1, "indvar")
  
  plot(margin)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/fVbmm.png" alt="Plot with expected confidence intervals"></p>
  
  <p>This gives me nice clean confidence intervals around the independent variable.
  However, as soon as I add in the state fixed effects, the confidence interval stretches essentially from 0 to 1, even though there remains a super strong relationship.</p>
  
  <pre><code>m2 &lt;- glm(depvar ~ indvar + state, data = data, family = "binomial")
  
  margin &lt;- ggeffect(m2, "indvar")
  
  plot(margin)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/CuK1h.png" alt="Plot with super wide confidence intervals"></p>
  
  <p>Thoughts much appreciated!</p>