[Matplotlib-users] Re: animation.FuncAnimation example --- how does it work?
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. -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
The documentation should say the number, not a number. This particular argument expects either a generator, an iterable, or an integer. If none is given, it will try and figure out something for itself. The integer is used to create a number generator, and so you effectively have an iterable that supplies the first argument to the animation function. Often times, the first argument to this function is just a frame index. It is quite possible that you don't need it at all, but it is a part of the defined API that the FuncAnimation assumes to be able to call the user-supplied function. Does that help? Ben Root shameless_plug P.S. - My new book Interactive Applications using Matplotlib has an entire chapter devoted to animations /shameless_plug On Thu, Apr 23, 2015 at 12:05 PM, Virgil Stokes v...@it.uu.se wrote: 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. -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
Can everyone please bring the level of snark/hostility down? Programming is frustrating, but antagonizing the mailing list does not help anyone. It is not well documented, but the signature for `func` is assumed to be `def function(required, *optional_positional)` see https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/animation.py#L1107 for the line where it actually gets called. The logic behind this is that the function needs to have some input to know what to draw (so the state about where in the sequence you are lives in the animation code, not in the supplied user code). For passing in the frame data you have several options. The first is to pass in an iterable of the data you want to be passed to the function (ex np.arange(5), image_stack, image_generator), basically anything where `it = iter(input); data = next(it)` 'does the right thing'. The second is to pass in a callable where repeated calls to `data = my_callable()` 'does the right thing' This would be useful if you want to reach out and hit some external hardware for you data each time the animation updates. The last is to pass in a number of frames, which gets converted into xrange(frames). In all cases, the Animation turns what ever your input is into an iterable which gets hit once pre frame (see https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/animation.py#L1047 for the code version of this paragraph). Tom PS was finishing this up as Ben's email came in On Thu, Apr 23, 2015 at 12:06 PM Virgil Stokes v...@it.uu.se wrote: 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.
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
Animation problem of Virgil Stokes. Since I began the answer sequence, here's a little more. If this overlaps other answers, I apologize. About the third parameter /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. I am not trying to accuse you of anything, I simply underline that if the documentation - as cited - mentions the word *generator*, and the program contains the argument *data_gen*, which is OBVIOUSLY a generator which *yields* some data, then this might have give you some clues concerning its meaning. 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. 1. Generators might be or not function arguments, keyword or not; this is not an issue here. Generators are entities which produce iterators. Here you have: *def data_gen(): while True: yield np.random.rand(10)* , and this is all. 2. When you see frames=None, etc., this doesn't absolutely mean that it is a kw parameter, just a positional parameter with a default value. Brendan Barnwell commented this already. If you look at the definition of the FuncAnimation class, which is readable, in the file ... matplotlib/animation.py, you will see *def __init__(self, fig, func, frames=None, init_func=None, fargs=None, save_count=None, **kwargs):** ** ...* which explicitly confirms this. I think that you got the answers you demanded. The FuncAnimation callback *requires* one argument, even if you don't use it. It may be the frame number (or index if you wish), or explicit, specific data, such as in your first example. If, as in your second example, the parameter passed is the frame index, and you want to see how you can use it, test this: *x=np.linspace(0,20,300)*** * def update(i):* ** ** *data=(np.sin(x+i/3)+1)/2* ** *line.set_ydata(data)* ** *** *** *ani = animation.FuncAnimation(fig, update, interval=40)* You should see a moving sinusoid. 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. I don't understand your reaction. I teach computer science for many years, and several times per week I suggest to my students to do this, to trace their programs. I trace mine. Nobody feels offended. You said: data is undefined. But it WAS DEFINED, you agree? So, printing its value was the most natural suggestion. You would immediately see that it had been generated by data_gen. Also, I recommend that you look upon the sources of Matplotlib from time to time. I do it regularly, it is nicely commented, and complements very well the documentation. Jerzy Karczmarczuk PS. Some blizzard around positional/keyword parameters in Python is quite persistent. Dive into Python of Mark Pilgrim covers this, and offers some useful references. See also this : https://www.python.org/dev/peps/pep-3102/ -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
Brendan, good catch, I didn't notice Virgil's confusion earlier. I think that is a good explanation. I remember getting very confused by all of that stuff back when I started in Python. I think mostly because I don't know of any other language that does argument handling like how Python does it. I learned it all by school-of-hard-knocks. Does anybody recommend a really good online reference that explains the ins-and-outs of positional and keyword arguments for newbies? Cheers! Ben Root On Thu, Apr 23, 2015 at 1:00 PM, Brendan Barnwell brenb...@brenbarn.net wrote: On 2015-04-23 03:22, Virgil Stokes wrote: 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. One thing I think may be misleading you is that you seem to be misunderstanding how positional and keyword arguments work in Python. Specifying a default value for an argument in a function definition doesn't mean that you can *only* pass it by keyword when you call it. Any named argument can always be passed positionally or by keyword (in Python 2). For instance, if I define a function like this: def foo(a, b=2): print a+b I can still call it like this: foo(8, 10) I can even call it like this (passing both arguments as keywords out of order) foo(b=10, a=8) Writing b=2 in the function definition doesn't so much make b a keyword argument as just specify a default value for b. So in the FuncAnimation documentation you mentioned, frames is not required to be a keyword argument, and can still be passed positionally. (In Python 3 there are keyword-only arguments, and even in Python 2 the variadic **kwargs syntax collects only keyword arguments, but those aren't involved as far as the frame argument here is concerned.) -- Brendan Barnwell Do not follow where the path may lead. Go, instead, where there is no path, and leave a trail. --author unknown -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
On 2015-04-23 03:22, Virgil Stokes wrote: 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. One thing I think may be misleading you is that you seem to be misunderstanding how positional and keyword arguments work in Python. Specifying a default value for an argument in a function definition doesn't mean that you can *only* pass it by keyword when you call it. Any named argument can always be passed positionally or by keyword (in Python 2). For instance, if I define a function like this: def foo(a, b=2): print a+b I can still call it like this: foo(8, 10) I can even call it like this (passing both arguments as keywords out of order) foo(b=10, a=8) Writing b=2 in the function definition doesn't so much make b a keyword argument as just specify a default value for b. So in the FuncAnimation documentation you mentioned, frames is not required to be a keyword argument, and can still be passed positionally. (In Python 3 there are keyword-only arguments, and even in Python 2 the variadic **kwargs syntax collects only keyword arguments, but those aren't involved as far as the frame argument here is concerned.) -- Brendan Barnwell Do not follow where the path may lead. Go, instead, where there is no path, and leave a trail. --author unknown -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF ___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
On 23-Apr-2015 18:48, Benjamin Root wrote: ... keeping conversation on-list ... The reason why you get that error is because you took out the argument from the call signature. But, FuncAnimation assumes that it can send in at least one argument. That argument is not optional, even if you aren't using it. So, animate() was called with an argument by FuncAnimation internally, but since animate() as defined by you did not have that argument, it fails. Ok --- thanks again for the clarification. Who knows, with a little help from this list, I might someday be able to create some useful animations with Matplotlib ;-) Cheers! Ben Root On Thu, Apr 23, 2015 at 12:32 PM, Virgil Stokes v...@it.uu.se mailto:v...@it.uu.se wrote: On 23-Apr-2015 18:25, Benjamin Root wrote: The documentation should say the number, not a number. This particular argument expects either a generator, an iterable, or an integer. If none is given, it will try and figure out something for itself. The integer is used to create a number generator, and so you effectively have an iterable that supplies the first argument to the animation function. Ok Benjamin :-) --- thanks for the clarification. Often times, the first argument to this function is just a frame index. It is quite possible that you don't need it at all, but it is a part of the defined API that the FuncAnimation assumes to be able to call the user-supplied function. Does that help? Yes, this does indeed help. But I am still puzzled by the error message given when I remove the argument to the animate function. Ben Root shameless_plug P.S. - My new book Interactive Applications using Matplotlib has an entire chapter devoted to animations /shameless_plug Thanks for this also Ben --- I will quite likely get this book. However, considering the complexity of Matplotlib --- only 174 pages bothers me a little. :-) On Thu, Apr 23, 2015 at 12:05 PM, Virgil Stokes v...@it.uu.se mailto:v...@it.uu.se wrote: 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;
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
... keeping conversation on-list ... The reason why you get that error is because you took out the argument from the call signature. But, FuncAnimation assumes that it can send in at least one argument. That argument is not optional, even if you aren't using it. So, animate() was called with an argument by FuncAnimation internally, but since animate() as defined by you did not have that argument, it fails. Cheers! Ben Root On Thu, Apr 23, 2015 at 12:32 PM, Virgil Stokes v...@it.uu.se wrote: On 23-Apr-2015 18:25, Benjamin Root wrote: The documentation should say the number, not a number. This particular argument expects either a generator, an iterable, or an integer. If none is given, it will try and figure out something for itself. The integer is used to create a number generator, and so you effectively have an iterable that supplies the first argument to the animation function. Ok Benjamin :-) --- thanks for the clarification. Often times, the first argument to this function is just a frame index. It is quite possible that you don't need it at all, but it is a part of the defined API that the FuncAnimation assumes to be able to call the user-supplied function. Does that help? Yes, this does indeed help. But I am still puzzled by the error message given when I remove the argument to the animate function. Ben Root shameless_plug P.S. - My new book Interactive Applications using Matplotlib has an entire chapter devoted to animations /shameless_plug On Thu, Apr 23, 2015 at 12:05 PM, Virgil Stokes v...@it.uu.se wrote: 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 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
[Matplotlib-users] animation.FuncAnimation example --- how does it work?
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 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. 2. data, the argument to the update function seems to be undefined. I would appreciate an explanation (in some detail) of how this code actually works. -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
Re: [Matplotlib-users] animation.FuncAnimation example --- how does it work?
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 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. The name data_gen could suggest its meaning (after having read the doc). Note please that the keyword parameters are specified extra. 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. Please, in such cases test your programs by adding some simple tracing contraptions, say, print(data) inside update. Jerzy Karczmarczuk -- BPM Camp - Free Virtual Workshop May 6th at 10am PDT/1PM EDT Develop your own process in accordance with the BPMN 2 standard Learn Process modeling best practices with Bonita BPM through live exercises http://www.bonitasoft.com/be-part-of-it/events/bpm-camp-virtual- event?utm_ source=Sourceforge_BPM_Camp_5_6_15utm_medium=emailutm_campaign=VA_SF___ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
