title: Reverse Z Axis on matplotlib 3D Plot
body: <p>How would one reverse the order on the z axis of a 3D plot (i.e. negative is up, and positive is down)? The following code produces a cone with the base pointing downward; is there a command (like <code>ax.reverse_zlim3d(True)</code> or something?) that can be used to change the tick order?</p>
  
  <p>The following code plots a cone with the base pointing downward.  I would like to reverse the z-axis order so that it plots with the base pointing up, like an ice cream cone, with -1 at the top of the graph instead of the bottom.</p>
  
  <pre><code>from matplotlib import pyplot as p
  from mpl_toolkits.mplot3d import Axes3D    # @UnusedImport
  
  import numpy as np
  from math import pi, cos, sin
  
  z = np.arange(0, 1, 0.02)
  theta = np.arange(0, 2 * pi + pi / 50, pi / 50)
  
  fig = p.figure()
  axes1 = fig.add_subplot(111, projection='3d')
  for zval in z:
      x = zval * np.array([cos(q) for q in theta])
      y = zval * np.array([sin(q) for q in theta])
      axes1.plot(x, y, -zval, 'b-')
  axes1.set_xlabel("x label")
  axes1.set_ylabel("y label")
  axes1.set_zlabel("z label")
  
  p.show()
  </code></pre>
  
  <p><img src="https://i.imgur.com/KEElFU7.png" alt="Cone Plot"></p>