Animate points with labels with matplotlib

Question

I\'ve got an animation with lines and now I want to label the points. I tried plt.annotate() and I tried plt.text() but the labes don\'t move. This

Answer 1

You have the return all objects that changed from your update function. So since your annotation changed it's position you should return it also:

line.set_data(newData)
annotation = plt.annotate('A0', xy=(newData[0][0],newData[1][0]))
return line, annotation

You can read more about matplotlib animations in this tutorial

You should also specify the init function so that the FuncAnimation knows which elements to remove from the plot when redrawing on the first update. So the full example would be:

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

# Create initial data
data = np.array([[1,2,3,4,5], [7,4,9,2,3]])

# Create figure and axes
fig = plt.figure()
ax = plt.axes(xlim=(0, 20), ylim=(0, 20))

# Create initial objects
line, = ax.plot([], [], 'r-')
annotation = ax.annotate('A0', xy=(data[0][0], data[1][0]))
annotation.set_animated(True)

# Create the init function that returns the objects
# that will change during the animation process
def init():
    return line, annotation

# Create the update function that returns all the
# objects that have changed
def update(num):
    newData = np.array([[1 + num, 2 + num / 2, 3, 4 - num / 4, 5 + num],
                        [7, 4, 9 + num / 3, 2, 3]])
    line.set_data(newData)
    # This is not working i 1.2.1
    # annotation.set_position((newData[0][0], newData[1][0]))
    annotation.xytext = (newData[0][0], newData[1][0])
    return line, annotation

anim = animation.FuncAnimation(fig, update, frames=25, init_func=init,
                               interval=200, blit=True)
plt.show()