title: error message when using mutate function in r
body: <p>receiving the following error message:
  Error in mutate_impl(.data, dots) : 
    Evaluation error: argument "no" is missing, with no default. </p>
  
  <pre><code> mutate(x,perfLev= ifelse(SS&lt; 1438, "Below Basic",
                     ifelse(SS&gt;= 1439 &amp; SS &lt;= 1499, "Basic",
                     ifelse(SS &gt;= 1500 &amp; SS &lt;= 1545, "Proficient",
                     ifelse(SS &gt;= 1546, "Advanced")))))
  </code></pre>