title: R correlation coefficient NA even if use= is included
body: <p>I am trying to correlate (pearson) two variable with some missing values. I am aware that I need to include use="complete.obs" in this situation. Here is the format of the command I used: </p>
  
  <pre><code>cor(data_frame, use="complete.obs")
  </code></pre>
  
  <p>I am getting NaN as correlation coefficients. I have tried <code>use="pairwise.complete.obs"</code> as well, with similar results.      </p>
  
  <p>Any advice would be much appreciated! Thank you</p>
  
  <p>Note: I am a beginner in R</p>