title: F# Filtering multiple years
body: <p>My objective is to find the total amount of sun for the following years - 1960,1970,1980,1990,2000,2010. The data comes from a txt file and year, month, maxt, mint, afday, rain and sun have already been defined and take the relevant element from the tuple, then it ignores the rest.</p>
  
  <pre><code>// Example
  let sun  (_,_,_,_,_,_,t) = t
  </code></pre>
  
  <p>I have found the total amount of sun for the year 1960. However, I am not sure how to find the remaining years. </p>
  
  <pre><code>let Q6 =
      ds |&gt; List.filter (fun s-&gt; year(s)=1960)
         |&gt; List.sumBy sun
  </code></pre>
  
  <p>The above method is a boolean so wouldn't work for multiple years, what is the best method?
  I believe the answer should be like this:</p>
  
  <pre><code>val Q6 : float list = [1434.4; 1441.8; 1393.0; 1653.0; 1599.5; 1510.2]
  </code></pre>