title: Create empty dataframe in R with same columns
body: <pre><code> names(U1)
  
  [1] "username"     "review_count" "forum_posts"  "age"          "avg_interval"
  [6] "avg_sim"      "class"
  </code></pre>
  
  <p>So how do I create an empty data frame U1.RN that will have same columns as U1?</p>