title: How to SUM the number of duplicates in a range by given value?
body: <p>A simple example as below:</p>
  
  <pre><code>Column A is the list containing all data
  Column B is the list of all unique data in Column A without duplicates
  Column C will be the number of duplicates for each item in Column B from Column A
  </code></pre>
  
  <p>How to write a easy formula for cells in Column C to sum each item in Column B from Column A?</p>
  
  <p>I used <code>=sum(lookup($a$1:$a$10=$B$1))</code> for C1 but received: <em>too few arguments for this function</em>.</p>
  
  <p><img src="https://i.stack.imgur.com/RPcma.jpg" alt="enter image description here"></p>