title: Why NaN/NA is NaN?
body: <pre><code>R&gt; 1/NA
  [1] NA
  R&gt; NaN/NA
  [1] NaN
  </code></pre>
  <p>A number divided by NA is NA. NaN is not even a number. So it is more reasonable to define NaN divided by NA as NA.</p>
  <p>I don't understand the logic of defining it as NaN. Is it a careful design choice of R? Or it is just a haphazard choice that was stuck at the birth of R or S.</p>
  <p>I don't need any guessed answer to this question. I need an authoritative answer from the original designers of R that carefully thought about this case.</p>