title: Element-wise variance of an iterator
body: <p>What's a numerically-stable way of taking the variance of an iterator elementwise? As an example, I would like to do something like</p>
  
  <pre><code>var((rand(4,2) for i in 1:10))
  </code></pre>
  
  <p>and get back a <code>(4,2)</code> matrix which is the variance in each coefficient. This throws an error using Julia's Base <code>var</code>. Is there a package that can handle this? Or an easy (and storage-efficient) way to do this using the Base Julia function? Or does one need to be developed on its own?</p>