Half violin plot in matplotlib

Question

Recently matplotlib has added a native support for violin plot. What I want to do is half-violin plot. I guess that it can be done changing the body the function is returning. Do you know how to plot half violin plot as in the example but using the new function from matplotlib?

Answer 1

Here simplify modifying the patches, clipping the values on the right or left

data1 = (np.random.normal(0, 1, size=10000), np.random.normal(0, 2, size=10000))
data2 = (np.random.normal(1, 1, size=10000), np.random.normal(1, 2, size=10000))

fig, ax = plt.subplots(figsize=(18, 7))

v1 = ax.violinplot(data1, points=100, positions=np.arange(0, len(data1)),
               showmeans=False, showextrema=False, showmedians=False)
for b in v1['bodies']:
    # get the center
    m = np.mean(b.get_paths()[0].vertices[:, 0])
    # modify the paths to not go further right than the center
    b.get_paths()[0].vertices[:, 0] = np.clip(b.get_paths()[0].vertices[:, 0], -np.inf, m)
    b.set_color('r')

v2 = ax.violinplot(data2, points=100, positions=np.arange(0, len(data2)), 
               showmeans=False, showextrema=False, showmedians=False)

for b in v2['bodies']:
    # get the center
    m = np.mean(b.get_paths()[0].vertices[:, 0])
    # modify the paths to not go further left than the center
    b.get_paths()[0].vertices[:, 0] = np.clip(b.get_paths()[0].vertices[:, 0], m, np.inf)
    b.set_color('b')

ax.legend([v1['bodies'][0],v2['bodies'][0]],['data1', 'data2'])