title: Preallocating a dataframe in R with date as the column class
body: <p>I want to preallocate space for dates in an R dataframe.  </p>
  
  <p>To preallocate space for characters and numbers, I would write</p>
  
  <pre><code>MyDataframe &lt;- data.frame(Name = character(10), 
                            Tickets  = numeric(10))
  </code></pre>
  
  <p>What would I add next to preallocate space for dates?
  This does not work...</p>
  
  <pre><code># DOES NOT WORK
  MyDataframe &lt;- data.frame(Name = character(10), 
                            Tickets  = numeric(10)
                            Date = Date(10))
  </code></pre>
  
  <p>Currently, I define the column as numeric, then coerce to dates, but this seems less than ideal.<br>
  Thanks</p>