title: What does the period mean when used with ~ (in a formula)?
body: <p>From the <a href="http://cran.r-project.org/web/packages/FSelector/FSelector.pdf" rel="noreferrer">FSelector manual</a>:</p>
  
  <pre><code>data(iris)
  subset &lt;- cfs(Species~., iris)
  f &lt;- as.simple.formula(subset, "Species")
  print(f)
  </code></pre>
  
  <p>Specifically, I mean the one in "Species~.".</p>
  
  <p>Now, it's awfully tough to Google how a bit of punctuation is used (for me anyway) and I couldn't anything. This code is unclear.</p>