title: Get vector angle by python
body: <p>I have a vector list. I want to get angle in each vector.</p>
  
  <pre><code>import numpy as np
  
  v = np.array([[-3, 4],
                [-2, -5],
                [2, 6],
                [3, -10]])
  
  inv = np.arctan(v[:, 1] / v[:, 0])
  degree = np.degrees(inv)
  print(degree)  # get [-53.13010235,  68.19859051,  71.56505118, -73.30075577]
  
  # use arctan2
  inv = np.arctan2(v[:, 1] / v[:, 0])
  degree = np.degrees(inv)
  print(degree)  # get [ 126.86989765, -111.80140949,   71.56505118,  -73.30075577]
  </code></pre>
  
  <p>but I want to get [127, 248 , 71, 286] (0~360 angle).
  How to solve?</p>