title: Passing a missing argument in R
body: <p>I'm writing a function in R that, among other things, subsets a data frame based on a vector of column names. I'm trying to exploit the default behavior of <code>[.data.frame</code> which will return all columns if the 'j' argument is missing. Is there a way to pass a missing argument through my wrapper function? Here's a bare bones example:</p>
  
  <pre><code>fixDataFrames &lt;- function(listOfDataFrames, columns){
      lapply(listOfDataFrames, function(x) x[,columns])
  }
  </code></pre>
  
  <p>If I do not specify a value for columns, I get an error when passing it to the <code>[</code> function: "columns argument is missing, with no default".</p>