Merge pull request #6814 from pd3/master

tacaswell · tacaswell · commit fc884742a1cf · 2016-10-11T10:11:36.000-04:00
DOC: Customize violin plot demo Add violin plot example with customized colors closes #6723
diff --git a/examples/statistics/customized_violin_demo.py b/examples/statistics/customized_violin_demo.py
@@ -0,0 +1,77 @@
+# Customizing violin plots
+#
+#
+
+import matplotlib.pyplot as plt
+import numpy as np
+
+
+# functions to calculate percentiles and adjacent values
+def percentile(vals, p):
+    N = len(vals)
+    n = p*(N+1)
+    k = int(n)
+    d = n-k
+    if k <= 0:
+        return vals[0]
+    if k >= N:
+        return vals[N-1]
+    return vals[k-1] + d*(vals[k] - vals[k-1])
+
+
+def adjacent_values(vals):
+    q1 = percentile(vals, 0.25)
+    q3 = percentile(vals, 0.75)
+    uav = q3 + (q3-q1)*1.5
+    if uav > vals[-1]:
+        uav = vals[-1]
+    if uav < q3:
+        uav = q3
+    lav = q1 - (q3-q1)*1.5
+    if lav < vals[0]:
+        lav = vals[0]
+    if lav > q1:
+        lav = q1
+    return [lav, uav]
+
+# create test data
+dat = [np.random.normal(0, std, 100) for std in range(6, 10)]
+lab = ['a', 'b', 'c', 'd']    # labels
+med = []    # medians
+iqr = []    # inter-quantile ranges
+avs = []    # upper and lower adjacent values
+for arr in dat:
+    sarr = sorted(arr)
+    med.append(percentile(sarr, 0.5))
+    iqr.append([percentile(sarr, 0.25), percentile(sarr, 0.75)])
+    avs.append(adjacent_values(sarr))
+
+# plot the violins
+fig, ax = plt.subplots(nrows=1, ncols=1, figsize=(7, 5))
+parts = ax.violinplot(dat, showmeans=False, showmedians=False,
+                      showextrema=False)
+
+# plot medians and averages
+for i in range(len(med)):
+    ax.plot([i+1, i+1], avs[i], '-', c='black', lw=1)
+    ax.plot([i+1, i+1], iqr[i], '-', c='black', lw=5)
+    ax.plot(i+1, med[i], 'o', mec='none', c='white', ms=6)
+
+# customize colors
+for pc in parts['bodies']:
+    pc.set_facecolor('#D43F3A')
+    pc.set_edgecolor('black')
+    pc.set_alpha(1)
+
+ax.get_xaxis().set_tick_params(direction='out')
+ax.xaxis.set_ticks_position('bottom')
+ax.set_xticks([x+1 for x in range(len(lab))])
+ax.set_xticklabels(lab)
+ax.set_xlim(0.25, len(lab)+0.75)
+ax.set_ylabel('ylabel')
+ax.set_xlabel('xlabel')
+ax.set_title('customized violin plot')
+
+plt.subplots_adjust(bottom=0.15)
+
+plt.show()
