title: Matlab: Conditional sum
body: <p>I want to calculate a conditional sum of a vector.</p>
  
  <p>Ex:</p>
  
  <p>A = [1, 2, 3, 4, 5, 6] <br>
  Condtional: a > 4<br>
  Result = 5 + 6 = 11</p>
  
  <p>How can I do this in Matlab?</p>