title: Creating dummy variables in a FF object
body: <p>I have an FFDF object that I'd like to create dummy variables in. Specifically, I have a separate vector of names and I want to make dummy variables if a name in that vector matches a name I have in a column vector in my FFDF. </p>
  
  <p>As an example, suppose I had this vector and this FFDF object: </p>
  
  <pre><code>Name
  1. Blow, Joe
  2. Smith, John
  3. Jones, Tom 
  etc....
  
  DonorName     CandidateName DonationAmount CandidateParty
  1   blow joe Bush, George W          3,000     Republican
  2   guy some  Obama, Barack          5,000       Democrat
  3 smith john    Reid, Harry          4,000       Democrat
  </code></pre>
  
  <p>What I'd like to do is create a separate column in the FFDF file and make it a 1 if a name in "Name" matches a name in "DonorName." Normally, I could use an ifelse() command, but the ff version, (ffifelse) is giving me this error: "test needs to be a logical/boolean ff vector." I should also add that I've coerced the first vector into an ffdf object using the as.ffdf() command. </p>
  
  <p>EDIT: </p>
  
  <p>I think I may finally have it working. This line of code seemed to do the trick.  </p>
  
  <pre><code>    ffdfobject$colname &lt;- ffifelse(ffdfobject$DonorName %in% otherffdfobj$name, 1,0)
  </code></pre>