title: convert list type to data frame type in R, data.frame and as.data.frame does not wok
body: <p>I have created A with command data.frame in R, but the data type of A is "list", and I have already tried to convert A to data frame with as.data.frame but it does work, anyone else has same experience? the code are below:</p>
  
  <pre><code>A &lt;- data.frame(rep(1,5), row.names=c("A","B","C","D","E"), check.rows = FALSE, check.names = FALSE)
  mode(A)
  A1 &lt;- as.data.frame(A)
  mode(A1)
  </code></pre>