title: Filter an array using a formula (without VBA)
body: <p>Is it possible to filter an array using a single formula (without autofilter, VBA, or additional columns)?</p>
  
  <p>For example, I have the following spreadsheet:</p>
  
  <pre><code>   A  | B     | C
   --------------------
  1| ID | Class | Value
  2| 1  | A     | V1
  3| 1  | B     | V2
  4| 2  | A     | V3
  5| 3  | B     | V4
  6| 3  | B     | V5
  </code></pre>
  
  <p>I want to use a subset of this array in VLOOKUP.  Namely, I only want to match against those rows where class is "B".  So I was hoping I could use something like the following</p>
  
  <pre><code>=VLOOKUP(A3, FILTER_FUNC(A:C, B="B"), 3, false)
  </code></pre>
  
  <p>where FILTER_FUNC is some type of function or expression that returns an array that only contains those rows that meet the condition.</p>