title: Calculate frequency of occurrence in an array using R
body: <p>I have an array </p>
  
  <pre><code>a &lt;- c(1,1,1,1,1,2,3,4,5,5,5,5,5,6,7,7,7,7)
  </code></pre>
  
  <p>I would like to use some command that would tell me which is the most frequent number in the array?</p>
  
  <p>is there a simple command for this?</p>