Thanks for your reply to my post, Jerzy.
On 23-Apr-2015 13:18, Jerzy Karczmarczuk wrote:
Le 23/04/2015 12:22, Virgil Stokes a écrit :
The following interesting example (random_data.py) is posted at:
http://matplotlib.org/1.4.2/examples/animation/random_data.html
import matplotlib.pyplot as plt
import matplotlib.animation as animation
import numpy as np
Yes, I forgot to include this
fig, ax = plt.subplots()
line, = ax.plot(np.random.rand(10))
ax.set_ylim(0, 1)
def update(data):
line.set_ydata(data)
return line,
def data_gen():
while True: yield np.random.rand(10)
ani = animation.FuncAnimation(fig, update, data_gen, interval=100)
plt.show()
This codes works; but, I am very confused by it. For example:
1. There are 3 positional arguments given for animation.FuncAnimation; but,
in the
API documentation for this class
(http://matplotlib.org/api/animation_api.html), only
two positional arguments are shown.
The third one is the third one,
"/frames/ can be a generator, an iterable, or a number of frames."
This makes very little sense to me --- what does "or a number of frames" mean?
The name "data_gen" could suggest its meaning (after having read the doc).
I am not sure what you are referencing as "the doc"; but I did read the
documentation several times and English is my native language.
Note please that the keyword parameters are specified extra.
I am aware of this. Perhaps, I am a Python dummy --- when I see something like
value = None in a Python API argument, I interpret this as a keyword argument
and not a generator.
2. data, the argument to the update function seems to be undefined.
FuncAnimation usually passes the frame number: 0, 1, 2, ... as the first
parameter of the update function, when "frames" is None, or the number of
frames. If - as here - the third parameter is a generator, it passes the
yielded data to update.
It may be used or not.
Ok, I understand that better now. But, you say "or *the number* of frames" but
the documentation reads "or *a number* of frames" --- what does this mean?
And I still do not understand how to use the first argument of the function to
be called for the animation. In another animation example (histogram.py), the
animation function is defined by:
def animate(i):
# simulate new data coming in
data = np.random.randn(1000
n, bins = np.histogram(data, 100)
top = bottom + n
verts[1::5,1] = top
verts[2::5,1] = top
This works of course; but, why is the "i" required? There is no other reference
to it in the entire script. If I remove it; i.e. use def animate(): I get the
following error:
TypeError: animate() takes no arguments (1 given)
I do not understand how this explains the fact that the function no longer has
any arguments. Please explain the meaning of this error message?
Please, in such cases test your programs by adding some simple tracing
contraptions, say, print(data) inside update.
I did this and more before posting my email. I would not have posted this unless
I thought it was necessary. And I thought one purpose of this user group was to
help people --- even if they ask a question which may be annoying or "stupid" in
some subscribers opinion. I try to remember what a very wise teacher once said
--- "there is no such thing as a stupid question".
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