Changed pie charts default shape to circle and added tests (#10914)

jerrylui803 · tacaswell · commit a10b90c1ef34 · 2018-03-31T16:04:27.000-04:00
API: set aspect in Axes.pie to be 'equal'

* Changed pie charts default shape to circle (instead of oval), and added tests

* Updated comments for default circular pie chart

* fix pep8

* removed unneccessary test case and updated docstring

* added what's new entry and edited docstring for pie

* fix pep8

* fixed typo
diff --git a/doc/users/next_whats_new/pie_chart_default.rst b/doc/users/next_whats_new/pie_chart_default.rst
@@ -0,0 +1,8 @@
+Pie charts are now circular by default
+--------------------------------------
+We acknowledge that the majority of people do not like egg-shaped pies.
+Therefore, an axes to which a pie chart is plotted will be set to have 
+equal aspect ratio by default. This ensures that the pie appears circular
+independent on the axes size or units. To revert to the previous behaviour
+you may set the axes' aspect to automatic, ax.set_aspect("auto") or 
+plt.axis("auto").
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -2624,7 +2624,10 @@ def pie(self, x, explode=None, labels=None, colors=None,
         -----
         The pie chart will probably look best if the figure and axes are
         square, or the Axes aspect is equal.
+        This method sets the aspect ratio of the axis to "equal".
+        The axes aspect ratio can be controlled with `Axes.set_aspect`.
         """
+        self.set_aspect('equal')
         x = np.array(x, np.float32)
 
         sx = x.sum()
diff --git a/lib/matplotlib/tests/baseline_images/test_axes/pie_default.png b/lib/matplotlib/tests/baseline_images/test_axes/pie_default.png
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4540,6 +4540,18 @@ def test_text_labelsize():
     ax.tick_params(direction='out')
 
 
+@image_comparison(baseline_images=['pie_default'], extensions=['png'])
+def test_pie_default():
+    # The slices will be ordered and plotted counter-clockwise.
+    labels = 'Frogs', 'Hogs', 'Dogs', 'Logs'
+    sizes = [15, 30, 45, 10]
+    colors = ['yellowgreen', 'gold', 'lightskyblue', 'lightcoral']
+    explode = (0, 0.1, 0, 0)  # only "explode" the 2nd slice (i.e. 'Hogs')
+    fig1, ax1 = plt.subplots(figsize=(8, 6))
+    pie1 = ax1.pie(sizes, explode=explode, labels=labels, colors=colors,
+                autopct='%1.1f%%', shadow=True, startangle=90)
+
+
 @image_comparison(baseline_images=['pie_linewidth_0', 'pie_linewidth_0',
                                    'pie_linewidth_0'],
                   extensions=['png'])
