title: How do I add a vector as a row to an existing data frame when the vector is longer than the data frame
body: <p>Apologies for a probably basic question but I can't seem to work out how to get this to work...</p>
  
  <p>I want to add a row vector to an existing data frame. However, often the new row will have more columns than the existing data frame and I would like to fill the missing column entries with NA or blank strings.</p>
  
  <p>For example, using this set up:</p>
  
  <pre><code>existing &lt;- data.frame(rbind(letters[1:5], letters[6:10]))
  new_row &lt;- letters[20:26]
  </code></pre>
  
  <p>I would like to end up with the following:</p>
  
  <pre><code>a  b  c  d  e  ""  ""
  f  g  h  i  j  ""  ""
  t  u  v  w  x  y   z
  </code></pre>
  
  <p>The rbind function only accept equal width vectors. I have heard of rbind.fill from the plyr package but this only works for two data frames. Does anyone have a simple way to do this?</p>
  
  <p>Many thanks
  Adrian</p>