title: 3d vectors in python
body: <p>The code below allows me to plot vectors at different vertical levels but these vectors do not have arrow heads attached to them.  I was wondering how should I modify this code so that I can get arrowheads at the end of the vectors?</p>
  
  <pre><code>#!/usr/bin/python
  
  import matplotlib.pyplot as plt
  from mpl_toolkits.mplot3d import Axes3D
  from matplotlib.patches import FancyArrowPatch
  import numpy as np
  from mpl_toolkits.mplot3d import proj3d
  
  fig = plt.figure()
  ax = fig.add_subplot(111, projection='3d')
  ax.plot([0,0.7], [0,0.5],zs=[1,1])
  ax.plot([0,-0.3], [0,0.7],zs=[2,2])
  ax.plot([0,-0.3],[0,0],zs=[3,3])
  
  ax.set_xlim([0,3])
  ax.set_ylim([3,0])
  ax.set_zlim([0,4])
  plt.show()
  </code></pre>