title: How can I create a conditional SUMPRODUCT formula for a horizontal set of timeseries data
body: <p>I'm attempting to use sumproduct on 2 sets of timeseries data that is formatted in the following way:</p>
  
  <p><strong>Array 1</strong></p>
  
  <pre><code>       | 01/01/2016 | 02/01/2016 | ...
  Stock1 | Price1a    | Price1b    |
  Stock2 | Price2a    | Price2b    |
  </code></pre>
  
  <p><strong>Array 2</strong></p>
  
  <pre><code>       | 01/01/2016 | 02/01/2016 | ...
  Stock1 | Volume1a   | Volume1b   |
  Stock2 | Volume2a   | Volume2b   |
  </code></pre>
  
  <p>Such that for a <em>given date</em>, the sumproduct formula will perform price * volume for all stocks in that date.</p>
  
  <p><strong>Example:</strong>
  For 01/01/2016, the formula will return Price1a * Volume1a + Price2a * Volume2a.</p>
  
  <p>Appreciate any help or questions in case it is unclear.</p>