title: Find GraphicsPlaceholder in a graphics array in MATLAB 2015
body: <p>Recently updated to MATLAB 2015 and it changed the way graphics handles are stored (I think). </p>
  
  <p>I store the handles of various lines on the same graph in a 2d array. In my previous version of MATLAB, any place I didn't fill was just a zero. Now that array is a graphics array and unfilled locations are "GraphicsPlaceholder". Is there any way to search the array to find where they are?</p>
  
  <p>For example, my list of handles is as follows:</p>
  
  <pre><code>    P= 
  
    2x7 graphics array:
  
    Columns 1 through 6
  
      Line                   Line                   Line                   Line                   Line                   Line               
      GraphicsPlaceholder    GraphicsPlaceholder    GraphicsPlaceholder    GraphicsPlaceholder    Line                   GraphicsPlaceholder
  </code></pre>
  
  <p>What I'd like to do is search and find which column is filled with lines instead of GraphicsPlaceholder. Ideally, it'd be something like</p>
  
  <pre><code>FUNCTION(P) = 
  
   1     1     1     1     1     1
   0     0     0     0     1     0
  </code></pre>
  
  <p>Thanks</p>