Make bar of pie example more explicit

QuLogic · QuLogic · commit 88433b806220 · 2022-01-24T18:53:28.000-05:00
... by saving and using the results from Axes method calls. Also,
replace the colour palette in the bar chart.
diff --git a/examples/pie_and_polar_charts/bar_of_pie.py b/examples/pie_and_polar_charts/bar_of_pie.py
@@ -19,40 +19,36 @@
 fig.subplots_adjust(wspace=0)
 
 # pie chart parameters
-ratios = [.27, .56, .17]
+overall_ratios = [.27, .56, .17]
 labels = ['Approve', 'Disapprove', 'Undecided']
 explode = [0.1, 0, 0]
 # rotate so that first wedge is split by the x-axis
-angle = -180 * ratios[0]
-ax1.pie(ratios, autopct='%1.1f%%', startangle=angle,
-        labels=labels, explode=explode)
+angle = -180 * overall_ratios[0]
+wedges, *_ = ax1.pie(overall_ratios, autopct='%1.1f%%', startangle=angle,
+                     labels=labels, explode=explode)
 
 # bar chart parameters
-
-xpos = 0
-bottom = 0
-ratios = [.33, .54, .07, .06]
+age_ratios = [.33, .54, .07, .06]
+age_labels = ['Under 35', '35-49', '50-65', 'Over 65']
+bottom = 1
 width = .2
-colors = [[.1, .3, .5], [.1, .3, .3], [.1, .3, .7], [.1, .3, .9]]
 
-for j in range(len(ratios)):
-    height = ratios[j]
-    ax2.bar(xpos, height, width, bottom=bottom, color=colors[j])
-    ypos = bottom + ax2.patches[j].get_height() / 2
-    bottom += height
-    ax2.text(xpos, ypos, "%d%%" % (ax2.patches[j].get_height() * 100),
-             ha='center')
+# Adding from the top matches the legend.
+for j, (height, label) in enumerate(reversed([*zip(age_ratios, age_labels)])):
+    bottom -= height
+    bc = ax2.bar(0, height, width, bottom=bottom, color='C0', label=label,
+                 alpha=0.1 + 0.25 * j)
+    ax2.bar_label(bc, labels=[f"{height:.0%}"], label_type='center')
 
 ax2.set_title('Age of approvers')
-ax2.legend(('50-65', 'Over 65', '35-49', 'Under 35'))
+ax2.legend()
 ax2.axis('off')
 ax2.set_xlim(- 2.5 * width, 2.5 * width)
 
 # use ConnectionPatch to draw lines between the two plots
-# get the wedge data
-theta1, theta2 = ax1.patches[0].theta1, ax1.patches[0].theta2
-center, r = ax1.patches[0].center, ax1.patches[0].r
-bar_height = sum([item.get_height() for item in ax2.patches])
+theta1, theta2 = wedges[0].theta1, wedges[0].theta2
+center, r = wedges[0].center, wedges[0].r
+bar_height = sum(age_ratios)
 
 # draw top connecting line
 x = r * np.cos(np.pi / 180 * theta2) + center[0]
