FuncAnimation update function not called

Question

I'm not quite getting how to create a class for animating data. Here is the gist:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation

x = np.arange(100).reshape((100, 1))
y = np.random.randn(100, 1)
xy = np.hstack((x, y))


class PlotData:
    def __init__(self):
        fig, ax = plt.subplots()
        fig.set_size_inches((11, 9))
        self.fig = fig
        self.ax = ax
        self.ln0, = ax.plot([], [])

    def init(self):
        self.ln0.set_data([], [])
        return(self.ln0, )

    def update(self, frame_no):
        data = xy[0:frame_no + 1]
        self.ln0.set_data(data[:, 0], data[:, 1])
        return(self.ln0, )


if __name__ == '__main__':
    my_plot = PlotData()
    anim = animation.FuncAnimation(my_plot.fig, my_plot.update,
                                   init_func=my_plot.init, blit=True,
                                   frames=99, interval=50)
    plt.show()

This only produces the init method output but not the update, so ends up a blank plot with no animation. What is going on?

Thomas Kühn · Accepted Answer · 2018-10-12T16:17:34.487

For me your code works perfectly fine. The only problem is that most of the data are outside of the plotting limits. If you adjust your plot limits like this:

class PlotData:
    def __init__(self):
        fig, ax = plt.subplots(figsize = (11,9))
        self.fig = fig
        self.ax = ax
        self.ax.set_xlim([0,100])
        self.ax.set_ylim([-3,3])
        self.ln0, = ax.plot([], [])

The line is animated just fine. If you want that the x- and y-limits are adjusted automatically, see this question on how to do it. However, if I recall correctly, this will only work properly with blit=False.

FuncAnimation update function not called

1 Answers1