Matplotlib FuncAnimation for scatter plot

Question

I am trying to use the FuncAnimation of Matplotlib to animate the display of one dot per frame of animation.

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Answer 1

The only problem with your example is how you fill the new coordinates in the animate function. set_offsets expects a Nx2 ndarray and you provide a tuple of two 1d arrays.

So just use this:

def animate(i):
    data = np.hstack((x[:i,np.newaxis], y[:i, np.newaxis]))
    scat.set_offsets(data)
    return scat,

And to save the animation you might want to call:

anim.save('animation.mp4')

Answer 2

Disclaimer, I wrote a library to try and make this easy but using ArtistAnimation, called celluloid. You basically write your visualization code as normal and simply take pictures after each frame is drawn. Here's a complete example:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
import numpy as np
from celluloid import Camera

fig = plt.figure()
camera = Camera(fig)

dots = 40
X, Y = np.random.rand(2, dots)
plt.xlim(X.min(), X.max())
plt.ylim(Y.min(), Y.max())
for x, y in zip(X, Y):
    plt.scatter(x, y)
    camera.snap()
anim = camera.animate(blit=True)
anim.save('dots.gif', writer='imagemagick')