title: How to extract vector from 3d numpy array?
body: <p>I have a set of numpy.arrays of NXM (two dimensions: Range and Azimuth). 
  I need to form a stack of three dimensions and extract a single dimension vector to compute a covariance matrix (the red vectors in the picture).</p>
  
  <p><a href="https://i.stack.imgur.com/gxnnw.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gxnnw.png" alt="enter image description here"></a></p>
  
  <p>How i do this efficiently and easy in Python?</p>