How to animate a scatter plot?

Question

I\'m trying to do an animation of a scatter plot where colors and size of the points changes at different stage of the animation. For data I have two numpy ndarray with an x

Answer 1

I wrote celluloid to make this easier. It's probably easiest to show by example:

import matplotlib.pyplot as plt
from matplotlib import cm
import numpy as np
from celluloid import Camera

numpoints = 10
points = np.random.random((2, numpoints))
colors = cm.rainbow(np.linspace(0, 1, numpoints))
camera = Camera(plt.figure())
for _ in range(100):
    points += 0.1 * (np.random.random((2, numpoints)) - .5)
    plt.scatter(*points, c=colors, s=100)
    camera.snap()
anim = camera.animate(blit=True)
anim.save('scatter.mp4')

It uses ArtistAnimation under the hood. camera.snap captures the current state of the figure which is used to create the frames in the animation.

Edit: To quantify how much memory this uses I ran it through memory_profiler.

Line #    Mem usage    Increment   Line Contents
================================================
    11     65.2 MiB     65.2 MiB   @profile
    12                             def main():
    13     65.2 MiB      0.0 MiB       numpoints = 10
    14     65.2 MiB      0.0 MiB       points = np.random.random((2, numpoints))
    15     65.2 MiB      0.1 MiB       colors = cm.rainbow(np.linspace(0, 1, numpoints))
    16     65.9 MiB      0.6 MiB       fig = plt.figure()
    17     65.9 MiB      0.0 MiB       camera = Camera(fig)
    18     67.8 MiB      0.0 MiB       for _ in range(100):
    19     67.8 MiB      0.0 MiB           points += 0.1 * (np.random.random((2, numpoints)) - .5)
    20     67.8 MiB      1.9 MiB           plt.scatter(*points, c=colors, s=100)
    21     67.8 MiB      0.0 MiB           camera.snap()
    22     70.1 MiB      2.3 MiB       anim = camera.animate(blit=True)
    23     72.1 MiB      1.9 MiB       anim.save('scatter.mp4')

To summarize this:

• Creating 100 plots used 1.9 MiB.
• Making the animation used 2.3 MiB.
• This method of making animations used 4.2 MiB of memory in sum.