title: Excel simple formula to work only on filtered results
body: <p>I have a set of data with over 1000 entries.
  I can filter these using the auto filter.
  At the bottom, I then have some simple formulas, for example AVERAGE() and QUARTILE().
  What I would like to achieve is that when I filter the data, the results from AVERAGE should change, so they should only take into account the visible data.</p>
  
  <p>I've been searching google and here, but can't seem to find anything like this, other than using "subtotal", but that's not for the formulas I want to use.</p>
  
  <p>Is this possible?
  Thanks,</p>