title: Google Data Studio: Average Number of Sessions based on selected country values
body: <p>Let's say that for the dimension <code>country</code> I have 4 values and for each of the 4 I have the respective number of <code>Sessions</code>. E.g.</p>
  
  <pre><code>+---------+----------+
  | country | Sessions |
  +---------+----------+
  | Italy   | 10       |
  | France  | 12       |
  | Germany | 14       |
  | Spain   | 16       |
  +---------+----------+
  </code></pre>
  
  <p>I want to compute and output in a scorecard the average number of <code>Sessions</code>, only for those specific countries. So, in the example, the output should be 13.</p>
  
  <p>I tried with the following calculated field but it doesn't work: </p>
  
  <pre><code>Sessions * AVG(CASE
      WHEN REGEXP_MATCH(country, '^Italy|France|Germany|Spain.*') THEN 1
      ELSE 0 END)
  </code></pre>