title: How do I create a calculation to view difference while adding a filter for an area code in Tableau?
body: <p><a href="https://i.stack.imgur.com/4nAY2.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4nAY2.png" alt="Image of my viz so far"></a></p>
  
  <p>Hi, I am new to tableau and working on a project:</p>
  
  <p>I have created a dumbell chart viz where total population is displayed between 2 years 2014 and 2017 for about 70 zip codes.</p>
  
  <p>I want to add a filter such that only the top 10 zip codes are shown which have the greatest decrease in population 2014-2017. </p>
  
  <p>Will a calculated field be required for this? Or is there a simple way to just filter?</p>
  
  <p>For example, I have filtered by Top 10 - variance but it is showing me incorrect figures</p>