title: NaNs produced when running summarySE
body: <h1>Running summarySE on species vs density dataset</h1>
  <p>My dataset is;</p>
  <pre><code>1   1   Zeacumantus  8.2222220
  2   2   Amphibola    1.2222220
  3   3   Cominella    1.7777778
  4   4   Zeacolpus    0.5555560
  5   5   Cominella    0.0000000
  6   6   Diloma       1.4444440
  7   7   Haminoea     0.1111110
  8   8   Austrovenus  82.0000000
  9   9   Macomona     7.7777780
  10  10  Nucula       0.6666670
  11  11  Halicarcinus 0.4444444
  12  12  Austrohelice 2.6666670
  13  13  Hemiplax     1.4444440
  14  14  Hemigrapsus  0.3333330
  15  15  worm         6.8888890
  16  16  Anthopleura  0.0000000
  17  17  Paracaudina  0.222222
  </code></pre>
  <p>the code I am trying to run is</p>
  <pre class="lang-r prettyprint-override"><code>library(Rmisc)
  
  sum = summarySE(high, measurevar=&quot;density&quot;, groupvars = &quot;species&quot;)
  </code></pre>
  <p>and it produces the error message</p>
  <pre class="lang-r prettyprint-override"><code>Warning message:
  In qt(conf.interval/2 + 0.5, datac$N - 1) : NaNs produced
  </code></pre>
  <p>I have run <code>which(is.nan())</code> for both &quot;species&quot; and &quot;density&quot; and both have produced <code>interger(0)</code></p>
  <p>Why is this happening?</p>