half (not split!) violin plots in seaborn


Currently seaborn offers functionality for split violinplots by setting split=True, according to a hue variable. I would like to make a 'half' violin plot, i.e. a plot where half of each violin is omitted. Such a plot depicts something similar to a pdf for each continuous variable, plotted on one side of each vertical line of each categorical variable only.

I have managed to trick seaborn to plot this with an extra data point outside the plotted range of values and an extra dummy hue, but I would like to know if this can be done without actually altering the dataset, e.g. within sns.violinplot() arguments.

For instance, this graph:

enter image description here

Was created by this snippet:

# imports
import pandas as pd
import seaborn as sns
import matplotlib.pyplot as plt

# load dataset from seaborn
datalist = sns.get_dataset_names()
dataset_name = 'iris'
if dataset_name in datalist:
    df = sns.load_dataset(dataset_name)
else:
    print("Dataset with name: " + dataset_name + " was not found in the available datasets online by seaborn.")

# prepare data
df2 = df.append([-999,-999,-999,-999,'setosa'])
df2['huecol'] = 0.0
df2['huecol'].iloc[-1]= -999

# plot
fig = plt.figure(figsize=(6,6))
sns.violinplot(x='species',y="sepal_width",
            split=True, hue ='huecol', inner = 'quartile',
            palette="pastel", data=df2, legend=False)
plt.title('iris')

# remove hue legend
leg = plt.gca().legend()
leg.remove()
plt.ylim([1,5.0])
plt.show()

Answers:


The answer is simply, no, it's not possible with seaborn without tricking it into thinking there is a hue present.

This answer shows how to do it in matplotlib and in principle the same can be applied to seaborn violinplots as well, namely to cut out half of the violin path.