title: numpy array - replace certain values
body: <p>I have yet to get my head around numpy array referencing.</p>
  
  <p>I have arrays where the first 2 columns will always have some negative values that are necessary and the remaining columns need to have their negative values substituted with 0s. I understand that there are various ways <a href="https://stackoverflow.com/questions/10335090/numpy-replace-negative-values-in-array">to do this</a>. The part that's baffling me is how to combine one of these methods with only doing it for the columns past 2.</p>
  
  <p>Example array:</p>
  
  <pre><code>[[x, y, flow, element1, element2, element3] [x, y, flow, element1, element2, element3] [x, y, flow, element1, element2, element3]]
  </code></pre>
  
  <p>Desired result would be that for the whole array, any of the values that are negative are replaced with 0 unless they are x or y. </p>