How to add time-varying title for Python matplotlib.animation?

Question

I am sorry for my poor English. I have a matrix datas (10000 times 5000). It includes 10000 cases of data and the dimension of each data is 5000. I want to make an animation to show each data one after another.

Following Code 1 works well.

(Code 1)

import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig = plt.figure()
ims = []

for i in range(10000):
    im = plt.plot(masks[i,:])    
    ims.append(im)

ani = animation.ArtistAnimation(fig, ims, interval=10)
plt.show()
ani.save('output.mp4', writer="ffmpeg")

I want to add the time-varying title to know which data (data index) is shown at a certain time.

And I wrote the following Code 2.

(Code 2)

import matplotlib.pyplot as plt
import matplotlib.animation as animation
fig = plt.figure()
ims = []

for i in range(10000):
    im = plt.plot(masks[i,:])    
    tl = 'Data number:' + str(i+1) # ***added***
    plt.title(tl) # ***added*** 
    ims.append(im)

ani = animation.ArtistAnimation(fig, ims, interval=10)
plt.show()
ani.save('output.mp4', writer="ffmpeg")

However, I got an animation whose title is always 'Data number: 10000'.

How can I write the code to add the time-varying title? I wrote plt.title(tl) before im = plt.plot(masks[i,:]) but nothing changed. Thank you for your help.

My environments are;

Python 3.6.9
matplitlib 3.3.3

Mr. T · Accepted Answer · 2022-02-10 02:36:03Z

1

We can imitate the figure title by annotating an axes object:

#test data generation
import numpy as np
np.random.seed(123)
masks = np.random.randn(10, 15)

#the animation routine starts here
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax = plt.subplots()
ims = []

#iterating over the array
for i in range(masks.shape[0]):
    #obtaining the Line2D object representing the line plot
    im, = ax.plot(masks[i,:], color="blue") 
    #creating a centered annotation text above the graph
    ann = ax.annotate(f"This is frame {i:.0f}.", (0.5, 1.03), xycoords="axes fraction", ha="center")
    #collecting both objects for the animation
    ims.append([im, ann])

ani = animation.ArtistAnimation(fig, ims, interval=300, repeat=False)
plt.show()

edited Feb 10, 2022 at 2:36

answered Jan 24, 2022 at 11:15

Mr. T

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