matplotlib while loop (matplotlib.animation?)

Question

I am plotting data with matplotlib.

I would like to watch the data being plotted over a few seconds time.

Current script (below) is close.. It closes the existing plot and makes a new plot including one additional data point for each while loop iteration.

If the "fig=" and "ax1=" statements are instead typed above the loop, I get only a blank plot.

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


def animate2(i):

    k=1

    #fig=plt.figure()
    #ax1=fig.add_subplot(1, 1, 1)

    while k <=len(i):

        fig=plt.figure()
        ax1=fig.add_subplot(1, 1, 1)

        ax1.clear
        ax1.plot(i[0:k, 0], i[0:k, 1])

        plt.show()
        time.sleep(1)
        k=k+1

Here the a sample np array I've used:

test_data=np.array([[3, 7],[1, 2],[8, 11],[5, -12],[20, 25], [-3, 30], [2,2], [17, 17]])

animate2(test_data)

Also, if you think matplotlib.animation would work better, please provide an example!

score 0 · Accepted Answer · edited May 23 '17 at 12:06

0

Using matplot.animation. It uses interval=miliseconds instead of time.sleep(). repeat stops looping. frames can be integer (number of frames) or list with numbers - every element from list is send to function as argument i.

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


def animate2(i):

    ax1.clear()
    ax1.plot(test_data[0:i, 0], test_data[0:i, 1])

# ---

test_data=np.array([[3, 7],[1, 2],[8, 11],[5, -12],[20, 25], [-3, 30], [2,2], [17, 17]])

fig = plt.figure()
ax1 = fig.add_subplot(1, 1, 1)

# create animation
animation.FuncAnimation(fig, animate2, frames=range(1, len(test_data)), interval=1000, repeat=False)

# start animation
plt.show()

You can also use fargs=tuplet-with-arguments to send own arguments to function

def animate2(i, data):

    ax1.clear()
    ax1.plot(data[0:i, 0], data[0:i, 1])

# ---

animation.FuncAnimation(fig, animate2, frames=range(1, len(test_data)), 
                         fargs=(test_data, ), interval=1000)

EDIT:

I used this code to generate animated GIF

(it needs imagemagick installed: https://stackoverflow.com/a/25143651/1832058)

# create animation
ani = animation.FuncAnimation(fig, animate2, frames=range(1, len(test_data)), interval=1000, repeat=False)

# save animation
ani.save('animation.gif', writer='imagemagick', fps=1)

and got this result

edited May 23 '17 at 12:06

Community

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1

answered Oct 27 '16 at 21:59

furas

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cool @furas , thanks for the help! Did you test this out? On my end, it still generates a blank, white plot.. – user80112 Oct 28 '16 at 13:25
My python environment is whatever comes with Enthought Canopy package, if that makes any difference – user80112 Oct 28 '16 at 13:27
I tested this code. Maybe you get some error message and his is why you don't get anything. – furas Oct 28 '16 at 13:34
btw you can put `print()` in `animate2` and other places to see which part is executed and which not. – furas Oct 28 '16 at 13:36
Okay, good to know. I have been testing things in jupyter notebook but don't see any error. I will continue trying.. thanks very much for your help – user80112 Oct 28 '16 at 13:43
see image in answer. – furas Oct 28 '16 at 13:46
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/126915/discussion-between-user80112-and-furas). – user80112 Oct 28 '16 at 14:10
got it! THANK YOU!! :D – user80112 Oct 28 '16 at 14:40

matplotlib while loop (matplotlib.animation?)

1 Answers1