title: OpenCV how to Group Rectangles
body: <p>I would like some help explaining how to use the opencv group rectangles function in python <a href="http://opencv.itseez.com/modules/objdetect/doc/cascade_classification.html?highlight=rejectlevels#grouprectangles" rel="noreferrer">SHOWN HERE</a>.</p>
  
  <p>I am running 2 haar cascades to detect objects in the image, but now I would like to merge the rectangles together.  I am guessing thats what the groupRectangles is used for.</p>
  
  <pre><code>cv2.groupRectangles(rectList, groupThreshold, eps, weights, levelWeights)
  </code></pre>
  
  <p>I am assuming that rectList is the vector returned by cv2.cascade.detectMultiScale()?
  Also I am not sure what the weights, and levelWeights are or what tehy are used for and would appreciate it if anyone could explain that, or show me where I can find out about it as i cant 
  find it in the documentation.</p>
  
  <p>Thanks for any help :-)</p>