Violin plot with inner median

violinplot-median.py

"""Violin plot with just the median drawn

By default, when plotting a split violin plot, the inner
box plot is for both splits. You can change this with `inner='quartile'`
to plot the quartiles for each split, but by default it uses a dashed
line (small dashes) for the 25 and 75-%ile and another dashed line
(big dashes) for the median, which is very ugly and cluttered.

This patching the `draw_quartiles` function to just draw the median
as a solid line.

This only works with seaborn 0.8. It does not work with seaborn 0.7
(init args have changed in `_ViolinPlotter`, as is their wont)
"""

from seaborn.categorical import _ViolinPlotter
import numpy as np
from matplotlib import pyplot as plt


class MyVPlot(_ViolinPlotter):
    def draw_quartiles(self, ax, data, support, density, center, split=False):
        """Draw the quartiles as lines at width of density."""
        q25, q50, q75 = np.percentile(data, [25, 50, 75])
        self.draw_to_density(ax, center, q50, support, density, split,
                             linewidth=self.linewidth, )


def my_violinplot(x=None, y=None, hue=None, data=None, order=None, hue_order=None,
                  bw="scott", cut=2, scale="area", scale_hue=True, gridsize=100,
                  width=.8, inner="box", split=False, dodge=True, orient=None,
                  linewidth=None, color=None, palette=None, saturation=.75,
                  ax=None, **kwargs):
    plotter = MyVPlot(x, y, hue, data, order, hue_order,
                      bw, cut, scale, scale_hue, gridsize,
                      width, inner, split, dodge, orient, linewidth,
                      color, palette, saturation)
    if ax is None:
        ax = plt.gca()

    plotter.plot(ax)
    return ax

Excellent! Thank you 👍