Backport PR #24843: Show that fill_between and span_where provide similar functionalities.

rcomer · meeseeksmachine · commit 5066a90dcccf · 2022-12-31T20:29:44.000Z
diff --git a/examples/lines_bars_and_markers/span_regions.py b/examples/lines_bars_and_markers/span_regions.py
@@ -1,12 +1,10 @@
 """
-================
-Using span_where
-================
+========================================================================
+Shade regions defined by a logical mask using fill_between or span_where
+========================================================================
 
-Illustrate some helper functions for shading regions where a logical
-mask is True.
-
-See `matplotlib.collections.BrokenBarHCollection.span_where`.
+Shade regions where a logical mask is True with `.Axes.fill_between` or with
+`matplotlib.collections.BrokenBarHCollection.span_where`.
 """
 
 import numpy as np
@@ -15,23 +13,22 @@
 
 
 t = np.arange(0.0, 2, 0.01)
-s1 = np.sin(2*np.pi*t)
-s2 = 1.2*np.sin(4*np.pi*t)
-
-
-fig, ax = plt.subplots()
-ax.set_title('using span_where')
-ax.plot(t, s1, color='black')
-ax.axhline(0, color='black', lw=2)
+s = np.sin(2*np.pi*t)
 
-collection = collections.BrokenBarHCollection.span_where(
-    t, ymin=0, ymax=1, where=s1 > 0, facecolor='green', alpha=0.5)
-ax.add_collection(collection)
+fig, axs = plt.subplots(2, sharex=True, sharey=True)
+for ax in axs:
+    ax.plot(t, s, color='black')
+    ax.axhline(0, color='black')
 
-collection = collections.BrokenBarHCollection.span_where(
-    t, ymin=-1, ymax=0, where=s1 < 0, facecolor='red', alpha=0.5)
-ax.add_collection(collection)
+axs[0].set_title('using fill_between')
+axs[0].fill_between(t, 1, where=s > 0, facecolor='green', alpha=.5)
+axs[0].fill_between(t, -1, where=s < 0, facecolor='red', alpha=.5)
 
+axs[1].set_title('using span_where')
+axs[1].add_collection(collections.BrokenBarHCollection.span_where(
+    t, ymin=0, ymax=1, where=s > 0, facecolor='green', alpha=0.5))
+axs[1].add_collection(collections.BrokenBarHCollection.span_where(
+    t, ymin=-1, ymax=0, where=s < 0, facecolor='red', alpha=0.5))
 
 plt.show()
 
@@ -43,7 +40,7 @@
 #    The use of the following functions, methods, classes and modules is shown
 #    in this example:
 #
+#    - `matplotlib.axes.Axes.fill_between`
 #    - `matplotlib.collections.BrokenBarHCollection`
 #    - `matplotlib.collections.BrokenBarHCollection.span_where`
 #    - `matplotlib.axes.Axes.add_collection`
-#    - `matplotlib.axes.Axes.axhline`
