Question

I have the following code.

import numpy as np
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
plt.ion()
plt.show()

mapping = defaultdict(partial(deque, maxlen=10))

My mapping structure contains a queues with x, y, z values. I want to plot only the point in queue so as the queue changes the plot should also change. How would I do that?

Note: This is challenging because the queue is of a bounded size and the plot has to reflect only whats in the queue.

Answer 1

The hacky way to do this is:

ln, = ax.plot(x,y,z)
# some code that updates the x,y,z values -> new_x,new_y,new_z
ln.remove
ln, = ax.plot(new_x,new_y,new_z)
plt.draw()

which removes the line with the old data and adds one with the new data.

If you are willing to write code that depends on the internals of matplotlib (which is a bad idea as the internal will likely change under you), you can also do this by:

ln._verts3d = new_x,new_y,new_z

Patch here for added a function to do this: https://github.com/matplotlib/matplotlib/pull/1629

The animation module nicely wraps up many of the things needed to do animation (including a way to stream output directly to ffmpeg), and there is a very nice tutorial.

Line3D docs, Line2D docs