title: Working with missing values in Deedle Time Series in F# (1)
body: <p>here is a small example where I want to deal with missing values on custom functions on series.</p>
  
  <p>suppose that i have obtained a series</p>
  
  <pre><code> series4;;
   val it : Series&lt;int,int opt&gt; =
   1 -&gt; 1         
   2 -&gt; 2         
   3 -&gt; 3         
   4 -&gt; &lt;missing&gt; 
  </code></pre>
  
  <p>for example, this way:</p>
  
  <pre><code> let series1 = Series.ofObservations [(1,1);(2,2);(3,3)]
   let series2 = Series.ofObservations [(1,2);(2,2);(3,1);(4,4)]
  
   let series3 = series1.Zip(series2,JoinKind.Outer);;
   let series4 = series3 |&gt; Series.mapValues fst
  </code></pre>
  
  <p>Then if i do,</p>
  
  <pre><code> Series.mapAll (fun v -&gt; match v with
                               | Some a -&gt; (a&gt;1)
                               | _-&gt; false) series4
  </code></pre>
  
  <p>that fails with </p>
  
  <blockquote>
    <p> System.Exception: Operation could not be completed due to earlier
    error  The type 'int option' does not match the type 'int opt'. See
    also input.fsx(4,42)-(4,49). at 4,42</p>
  </blockquote>
  
  <p>while i would like the result to be</p>
  
  <pre><code>val it : Series&lt;int,bool opt&gt; =
       1 -&gt; false        
       2 -&gt; true         
       3 -&gt; true         
       4 -&gt; false
  </code></pre>
  
  <p>even better would be to able to get a result like</p>
  
  <pre><code>val it : Series&lt;int,int opt&gt; =
       1 -&gt; false         
       2 -&gt; true         
       3 -&gt; true         
       4 -&gt; &lt;missing&gt; 
  </code></pre>
  
  <p>what would be the right syntax there ? ideally if there is a <code>&lt;missing&gt;</code> value, i would like a <code>&lt;missing&gt;</code> value for the same key in the new series</p>
  
  <p>basically i need to do pattern matching on <code>int opt</code> type </p>
  
  <p>Bonus question: is there are vectorized operator in Deedle for some usual operators such like ">" ? 
  (series1 > series2) when both series have the same key types would return a new series of boolean (option ?)type</p>
  
  <p>thanks</p>