title: Counting number of occurrences in column?
body: <p>What would be a good approach to calculate the number of occurrences in a spreadsheet column? Can this be done with a single <em>array formula</em>?</p>
  
  <p>Example (column <code>A</code> is <em>input</em>, columns <code>B</code> and <code>C</code> are <em>to be auto-generated</em>):</p>
  
  <pre><code>|   A   |   B   |   C   |
  +-------+-------+-------+
  | Name  | Name  | Count |
  +-------+-------+-------+
  | Joe   | Joe   |     2 |
  | Lisa  | Lisa  |     3 |
  | Jenny | Jenny |     2 |
  | Lisa  |       |       |
  | Lisa  |       |       |
  | Joe   |       |       |
  | Jenny |       |       |
  </code></pre>