title: Efficient MATLAB cart2sph and sph2cart functions in python
body: <p>I translated the MATLAB cart2sph and sph2cart functions to python in this way.</p>
  
  <pre><code>import numpy as np
  
  def cart2sph(x,y,z):
      azimuth = np.arctan2(y,x)
      elevation = np.arctan2(z,np.sqrt(x**2 + y**2))
      r = np.sqrt(x**2 + y**2 + z**2)
      return azimuth, elevation, r
  
  def sph2cart(azimuth,elevation,r):
      x = r * np.cos(elevation) * np.cos(azimuth)
      y = r * np.cos(elevation) * np.sin(azimuth)
      z = r * np.sin(elevation)
      return x, y, z
  </code></pre>
  
  <p>I didn't find any library in numpy that translate the MATLAB change of coordinates so I write them for my self.
  Is there in numpy a more efficient way in terms of execution time to write this fuctions?</p>