Matplotlib error Line2d object s not iterable error in tkinter callback nothing shows up

Question

The code is shown below. I am attempting to animate using vectors calculated earlier a figure window is opened so i know it gets this far and the vectors are being calclated correctly. But matplotlib oututs nothing but the figure window I have no idea why. Please help.

#finally animateing
fig = plt.figure()
ax = plt.axes(xlim = (-1000,1000) ,ylim = (-1000,1000))#limits were arbitrary
#line = ax.plot([],[])
line, = ax.plot([], [], lw=2)

# initialization function: plot the background of each frame
def init():
    line.set_data([], [])
    return line,


def animate(i):
 x = time_vec[i]
 y = complex_vec[i]
 #y1 = real_vec[i] 
 #y2 = modulus_vec[i]
 line.set_data(x,y)
 #line.set_data(x,y1)
 #line.set_data(x,y2) 
 return line,

animation_object = animation.FuncAnimation(fig, animate, init_func= init, frames = num_files,interval = 30, blit = True)

#turnn this line on to save as mp4
#anim.save("give it a name.mp4", fps = 30, extra-args = ['vcodec', 'libx264'])
plt.show()

THE FULL ERROR MESSAGE IS SHOWN BELOW

    Traceback (most recent call last):
  File "the_animation.py", line 71, in <module>
    plt.show()
  File "/usr/lib/pymodules/python2.7/matplotlib/pyplot.py", line 145,     in show
    _show(*args, **kw)
  File "/usr/lib/pymodules/python2.7/matplotlib/backend_bases.py",     line 117, in __call__
    self.mainloop()
  File     "/usr/lib/pymodules/python2.7/matplotlib/backends/backend_tkagg.py", line     69, in mainloop
    Tk.mainloop()
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 366, in mainloop
    _default_root.tk.mainloop(n)
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1484, in __call__
    def __call__(self, *args):

MINIMAL EXAMPLE

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
complex_vec = np.arange(5,6,.001)
real_vec = np.arange(7,8,.001)
time_vec = np.arange(0,1,.001)
num_files = np.size(time_vec)
#creating the modulus vector
modulus_vec = np.zeros(np.shape(complex_vec))
for k in range (0,complex_vec.size):
    a = complex_vec[k]
    b = real_vec[k]
    calc_modulus = np.sqrt(a**2 + b**2)
    modulus_vec[k] = calc_modulus
#finally animateing
fig = plt.figure()
ax = plt.axes(xlim = (-1000,1000) ,ylim = (-1000,1000))#limits were     arbitrary
#line = ax.plot([],[])
line, = ax.plot([], [], lw=2)

# initialization function: plot the background of each frame
def init():
    line.set_data([], [])
    return line,


def animate(i):
    x = time_vec[i]
    y = complex_vec[i]
    y1 = real_vec[i] 
    y2 = modulus_vec[i]
    line.set_data(x,y)
    line.set_data(x,y1)
    line.set_data(x,y2) 
    return line,

animation_object = animation.FuncAnimation(fig, animate, init_func= init, frames = num_files,interval = 30, blit = True)

#turnn this line on to save as mp4
#anim.save("give it a name.mp4", fps = 30, extra-args = ['vcodec',     'libx264'])
plt.show()

thats the even weirder part i will post the erroro message in just a moment — loma
– loma, Commented Jul 26, 2015 at 21:34
@Ioma you sure that's the full error? Because your error output has no error — Syntactic Fructose
– Syntactic Fructose, Commented Jul 26, 2015 at 21:48
you are right i suppossed that because nothing was showing up i would get an error but this just pops up so i assumed it was an error but I guess not however I am realy confused now because even after running for 2 hrs it still does not show anything just the figure window no axes nothing — loma
– loma, Commented Jul 26, 2015 at 21:51
@Ioma do you have some sort of minimal example you can post or link to this file if it's a single script? it's difficult to debug with no solid error output or access to the file — Syntactic Fructose
– Syntactic Fructose, Commented Jul 26, 2015 at 21:54

Syntactic Fructose · Accepted Answer · 2015-07-27 00:10:08Z

The problem here is in your animate function, you're using set_data multiple times which does not do what you think it does. You're using it like an append, when it's a set. The arguments should be two arrays, containing the respective x and y values for that line. This will animate your minimal example:

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

complex_vec = np.arange(5,6,.001)
real_vec = np.arange(7,8,.001)
time_vec = np.arange(0,1,.001)
num_files = np.size(time_vec)

#creating the modulus vector
modulus_vec = np.zeros(np.shape(complex_vec))
for k in range (0,complex_vec.size):
    a = complex_vec[k]
    b = real_vec[k]
    calc_modulus = np.sqrt(a**2 + b**2)
    modulus_vec[k] = calc_modulus

#finally animateing
fig = plt.figure()
ax = plt.axes(xlim = (-1,1) ,ylim = (-1,15))#limits were     arbitrary
#line = ax.plot([],[])
line, = ax.plot([], [], lw=2)

# initialization function: plot the background of each frame
def init():
    line.set_data([], [])
    return line,

def animate(i):
    x = time_vec[i]
    y = complex_vec[i]
    y1 = real_vec[i] 
    y2 = modulus_vec[i]
    # notice we are only calling set_data once, and bundling the y values into an array
    line.set_data(x,np.array([y, y1, y2]))
    return line,

animation_object = animation.FuncAnimation(fig, 
                                           animate, 
                                           init_func= init, 
                                           frames = num_files,
                                           interval = 30, 
                                           blit = True)

#turnn this line on to save as mp4
#anim.save("give it a name.mp4", fps = 30, extra-args = ['vcodec',     'libx264'])
plt.show()

Your previous attempt was setting the x and y values, then overwriting the previous with a new x and y, then doing that once again.

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