Cleanup animation examples

I thought that the animation examples section was a bit of an
unstructured mess so I tried to reorganize it somewhat.  The new list of
examples is

simple examples
===============
animation_demo: plt.pause example
simple_anim: FuncAnimation example
dynamic_image: FuncAnimation example
dynamic_image2: ArtistAnimation example

intermediate examples
=====================
strip_chart: FuncAnimation example

advanced examples
=================
histogram: animating a composite artist (namely, a histogram)

nice examples
=============
bayes: FuncAnimation example
double_pendulum: FuncAnimation example, skipped as needing scipy
random_walk (renamed from simple_3danim): FuncAnimation example
rain: FuncAnimation example
unchained: FuncAnimation example

movie writing
=============
frame_grabbing_sgskip (renamed from moviewriter_sgskip.py)

removed
=======
animate_decay: overlaps with simple_anim
basic_example: equivalent to {simple_anim + dynamic_image2}
basic_example_writer_sgskip: split as comments to
  simple_anim/dynamic_image/dynamic_image2
random_data: overlaps with simple_anim, though using a generator
subplots: relies on subclassing private attributes of TimedAnimation, would
  better be replaced by a FuncAnimation example, overly complex

doc/api/animation_api.rst

@@ -1,6 +1,6 @@
-======================
- ``animation`` module
-======================
+*********
+animation
+*********
 
 .. automodule:: matplotlib.animation
    :no-members:
@@ -11,10 +11,6 @@
    :local:
    :backlinks: entry
 
-
-Animation
-=========
-
 The easiest way to make a live animation in matplotlib is to use one of the
 `Animation` classes.
 
@@ -37,7 +33,6 @@ To save an animation to disk use `Animation.save` or `Animation.to_html5_video`
 See :ref:`ani_writer_classes` below for details about what movie formats are
 supported.
 
-
 ``FuncAnimation``
 -----------------
 
@@ -48,7 +43,6 @@ The inner workings of `FuncAnimation` is more-or-less::
      fig.canvas.draw_idle()
      fig.canvas.start_event_loop(interval)
 
-
 with details to handle 'blitting' (to dramatically improve the live
 performance), to be non-blocking, not repeatedly start/stop the GUI
 event loop, handle repeats, multiple animated axes, and easily save
@@ -122,54 +116,40 @@ artist at a global scope and let Python sort things out.  For example ::
                        init_func=init, blit=True)
    plt.show()
 
-
 The second method is to us `functools.partial` to 'bind' artists to
 function.  A third method is to use closures to build up the required
 artists and functions.  A fourth method is to create a class.
 
-
-
-
 Examples
 ~~~~~~~~
 
 .. toctree::
    :maxdepth: 1
 
-   ../gallery/animation/animate_decay
-   ../gallery/animation/bayes_update_sgskip
-   ../gallery/animation/double_pendulum_animated_sgskip
+   ../gallery/animation/bayes_update
+   ../gallery/animation/double_pendulum_sgskip
    ../gallery/animation/dynamic_image
    ../gallery/animation/histogram
    ../gallery/animation/rain
-   ../gallery/animation/random_data
-   ../gallery/animation/simple_3danim
+   ../gallery/animation/random_walk
    ../gallery/animation/simple_anim
-   ../gallery/animation/strip_chart_demo
+   ../gallery/animation/strip_chart
    ../gallery/animation/unchained
 
 ``ArtistAnimation``
 -------------------
 
-
 Examples
 ~~~~~~~~
 
 .. toctree::
    :maxdepth: 1
 
-   ../gallery/animation/basic_example
-   ../gallery/animation/basic_example_writer_sgskip
    ../gallery/animation/dynamic_image2
 
-
-
-
 Writer Classes
 ==============
 
-
-
 The provided writers fall into two broad categories: pipe-based and
 file-based.  The pipe-based writers stream the captured frames over a
 pipe to an external process.  The pipe-based variants tend to be more
@@ -179,7 +159,6 @@ performant, but may not work on all systems.
    :toctree: _as_gen
    :nosignatures:
 
-
    FFMpegWriter
    ImageMagickFileWriter
    AVConvWriter
@@ -196,7 +175,6 @@ slower, these writers can be easier to debug.
    ImageMagickWriter
    AVConvFileWriter
 
-
 Fundamentally, a `MovieWriter` provides a way to grab sequential frames
 from the same underlying `~matplotlib.figure.Figure` object.  The base
 class `MovieWriter` implements 3 methods and a context manager.  The
@@ -215,45 +193,39 @@ file to disk.  For example ::
        moviewriter.grab_frame()
    moviewriter.finish()
 
-
-If using the writer classes directly (not through `Animation.save`), it is strongly encouraged
-to use the `~MovieWriter.saving` context manager ::
+If using the writer classes directly (not through `Animation.save`), it is
+strongly encouraged to use the `~MovieWriter.saving` context manager ::
 
   with moviewriter.saving(fig, 'myfile.mp4', dpi=100):
       for j in range(n):
           update_figure(n)
           moviewriter.grab_frame()
 
-
 to ensures that setup and cleanup are performed as necessary.
 
+Examples
+~~~~~~~~
 
-:ref:`sphx_glr_gallery_animation_moviewriter_sgskip.py`
+.. toctree::
+   :maxdepth: 1
 
+   ../gallery/animation/frame_grabbing_sgskip
 
 .. _ani_writer_classes:
 
 Helper Classes
 ==============
 
-
 Animation Base Classes
 ----------------------
 
-
 .. autosummary::
    :toctree: _as_gen
    :nosignatures:
 
    Animation
    TimedAnimation
 
-
-Custom Animation classes
-------------------------
-
-:ref:`sphx_glr_gallery_animation_subplots.py`
-
 Writer Registry
 ---------------
 
@@ -280,7 +252,7 @@ To reduce code duplication base classes
    MovieWriter
    FileMovieWriter
 
-and mixins are provided
+and mixins
 
 .. autosummary::
    :toctree: _as_gen
@@ -290,9 +262,9 @@ and mixins are provided
    FFMpegBase
    ImageMagickBase
 
-See the source code for how to easily implement new `MovieWriter`
-classes.
+are provided.
 
+See the source code for how to easily implement new `MovieWriter` classes.
 
 Inheritance Diagrams
 ====================

examples/animation/bayes_update_sgskip.py → examples/animation/bayes_update.py

@@ -9,13 +9,18 @@
 distribution should converge.
 """
 
-# update a distribution based on new data.
+import math
+
 import numpy as np
 import matplotlib.pyplot as plt
-import scipy.stats as ss
 from matplotlib.animation import FuncAnimation
 
 
+def beta_pdf(x, a, b):
+    return (x**(a-1) * (1-x)**(b-1) * math.gamma(a + b)
+            / (math.gamma(a) * math.gamma(b)))
+
+
 class UpdateDist(object):
     def __init__(self, ax, prob=0.5):
         self.success = 0
@@ -47,7 +52,7 @@ def __call__(self, i):
         # Choose success based on exceed a threshold with a uniform pick
         if np.random.rand(1,) < self.prob:
             self.success += 1
-        y = ss.beta.pdf(self.x, self.success + 1, (i - self.success) + 1)
+        y = beta_pdf(self.x, self.success + 1, (i - self.success) + 1)
         self.line.set_data(self.x, y)
         return self.line,
 

examples/animation/double_pendulum_animated_sgskip.py → examples/animation/double_pendulum_sgskip.py

@@ -94,5 +94,4 @@ def animate(i):
 ani = animation.FuncAnimation(fig, animate, np.arange(1, len(y)),
                               interval=25, blit=True, init_func=init)
 
-# ani.save('double_pendulum.mp4', fps=15)
 plt.show()