Fix example for line animation

chahak13 · chahak13 · commit 9a0e85e351a2 · 2022-10-29T17:44:25.000-05:00
The animation for Lines2D was not showing the animation properly but was
showing just the final frame. Adding an init function resolved this
issue and the animation appears correctly now.
diff --git a/tutorials/introductory/animation_tutorial.py b/tutorials/introductory/animation_tutorial.py
@@ -21,10 +21,10 @@
 # The process of animation can be thought about in 2 different ways:
 #
 # - :class:`~matplotlib.animation.FuncAnimation`: Generate data for first
-# frame and then modify this data for each frame to create an animated plot.
+#   frame and then modify this data for each frame to create an animated plot.
 #
 # - :class:`~matplotlib.animation.FuncAnimation`: Generate a list (iterable)
-# of artists that will draw in each frame in the animation.
+#   of artists that will draw in each frame in the animation.
 #
 # :class:`~matplotlib.animation.FuncAnimation` is more efficient in terms of
 # speed and memory as it draws an artist once and then modifies it. On the
@@ -63,8 +63,15 @@
 xdata, ydata = [], []
 (line,) = ax.plot(xdata, ydata, c="b")
 ax.grid()
-ax.set_ylim(-1, 1)
-ax.set_xlim(0, 10)
+
+
+def init():
+    ax.set_ylim(-1.1, 1.1)
+    ax.set_xlim(0, 5)
+    del xdata[:]
+    del ydata[:]
+    line.set_data(xdata, ydata)
+    return line,
 
 
 def update(frame):
@@ -77,7 +84,8 @@ def update(frame):
     return (line,)
 
 
-ani = animation.FuncAnimation(fig=fig, func=update, interval=30)
+ani = animation.FuncAnimation(fig=fig, func=update,
+                              interval=30, init_func=init)
 plt.show()
 
 ###############################################################################
@@ -90,7 +98,7 @@ def update(frame):
 
 fig, ax = plt.subplots()
 rng = np.random.default_rng()
-t = np.linspace(-4, 4, 1000)
+t = np.linspace(-4, 4, 400)
 a, b = 3, 2
 delta = np.pi / 2
 
@@ -110,7 +118,7 @@ def update(frame):
     return (scat,)
 
 
-ani = animation.FuncAnimation(fig=fig, func=update, interval=30)
+ani = animation.FuncAnimation(fig=fig, func=update, frames=400, interval=30)
 plt.show()
 
 
@@ -169,21 +177,21 @@ def update(frame):
 # by all writers. There are 4 major types of writers:
 #
 # - :class:`~matplotlib.animation.PillowWriter` - Uses the Pillow library to
-# create the animation.
+#   create the animation.
 #
 # - :class:`~matplotlib.animation.HTMLWriter` - Used to create JS-based
-# animations.
+#   animations.
 #
 # - Pipe-based writers - :class:`~matplotlib.animation.FFMpegWriter` and
-# :class:`~matplotlib.animation.ImageMagickWriter` are pipe based writers.
-# These writers pipe each frame to the utility (*ffmpeg* / *imagemagick*) which
-# then stitches all of them together to create the animation.
+#   :class:`~matplotlib.animation.ImageMagickWriter` are pipe based writers.
+#   These writers pipe each frame to the utility (*ffmpeg* / *imagemagick*)
+#   which then stitches all of them together to create the animation.
 #
 # - File-based writers - :class:`~matplotlib.animation.FFMpegFileWriter` and
-# :class:`~matplotlib.animation.ImageMagickFileWriter` are examples of
-# file-based writers. These writers are slower than their standard writers but
-# are more useful for debugging as they save each frame in a file before
-# stitching them together into an animation.
+#   :class:`~matplotlib.animation.ImageMagickFileWriter` are examples of
+#   file-based writers. These writers are slower than their standard writers
+#   but are more useful for debugging as they save each frame in a file before
+#   stitching them together into an animation.
 #
 # ================================================  ===========================
 # Writer                                            Supported Formats
