title: Can't extract test statistics by $teststat from list in R
body: <p>I try to extract test statistics by <code>$teststat</code> from a test that I have run 10 000 times, but than I encounter the problem:</p>
  
  <pre><code>library(urca)
  df.test&lt;-replicate(10000,ur.df(cumsum(rnorm(n=100, mean=0))))
  </code></pre>
  
  <p>but command </p>
  
  <pre><code>df.test$teststats
  </code></pre>
  
  <p>gives output: <code>NULL</code></p>
  
  <p>Can anybody help?</p>