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Violin plots

Sahil Parrvez

9 months ago

Violin plots | insideAIML
Table of Contents
  • Introduction
  • Make a violin plot
  • Violin Plot Basic Example

Introduction

          Violin plots are similar to box plots, but they also show at different values ,the probability density of data.A marker for the median of the data and a box indicating the interquartile range are included in these plots, as in the standard box plots. Overlaid on this box plot is a kernel density estimation. It used to represent comparison of a variable distribution (or sample distribution) across different "categories".
Violin plots | Insideaiml
A violin plot is more informative than a plain box plot. In fact while a box plot only shows summary statistics such as mean/median and interquartile ranges, the violin plot shows the full distribution of the data.

Make a violin plot

          Create a violin diagram for each column in the data set or each vector in the sequence data set. Each filled area is stretched to represent the entire range of data, with optional lines at the mean, median, minimum, maximum, and custom quantiles.
matplotlib.pyplot.violinplot(dataset, positions=None, vert=True, widths=0.5, showmeans=False, showextrema=True, showmedians=False, quantiles=None, points=100, bw_method=None, *, data=None)
Parameters :
  • dataset : Array or a sequence of vectors.
                      The input data.
  • positions : array-like, default: [1, 2, ..., n]
                       The positions of the violins. The ticks and limits are automatically set to match the positions.
  • vert : bool, default: True.
                        If true, creates a vertical violin plot. Otherwise, creates a horizontal violin plot.
  • width : sarray-like, default: 0.5
                         Either a scalar or a vector that sets the maximal width of each violin. The default is 0.5, which                                 uses about half of the available horizontal space.
  • showmeans : bool, default: False
                        If True, will toggle rendering of the means.
  • showextrema : bool, default: True
                        If True, will toggle rendering of the extrema.
  • showmedians : bool, default: False
                        If True, will toggle rendering of the medians.
  • quantiles : array-like, default: None
                        If not None, set a list of floats in interval [0, 1] for each violin, which stands for the quantiles that                               will be rendered for that violin.
  • points : int, default: 100
                        Defines the number of points to evaluate each of the gaussian kernel density estimations at.
  • bw_method : str, scalar or callable, optional
                       The method used to calculate the estimator bandwidth. This can be 'scott', 'silverman', a scalar                             constant or a callable. If a scalar, this will be used directly as kde.factor. If a callable, it should
                       take a GaussianKDE instance as its only parameter and return a scalar. If None (default), 'scott' is                         used.
  • data : indexable object, optional
                       If given, the following parameters also accept a string s, which is interpreted as data[s] (unless                               this  raises an exception):
                       dataset
Returns
dict
A dictionary mapping each component of the violinplot to a list of the corresponding collection instances created. The dictionary has the following keys:
  • bodies : A list of the PolyCollection instances containing the filled area of each violin.
  • cmeans : A LineCollection instance that marks the mean values of each of the violin's distribution.
  • cmins : A LineCollection instance that marks the bottom of each violin's distribution.
  • cmaxes : A LineCollection instance that marks the top of each violin's distribution.
  • cbars : A LineCollection instance that marks the centers of each violin's distribution.
  • cmedians : A LineCollection instance that marks the median values of each of the violin's distribution.
  • cquantiles : A LineCollection instance created to identify the quantile values of each of the violin's distribution.

Violin Plot Basic Example:

import numpy as np
import matplotlib.pyplot as plt

# generate some random data
sample1= np.random.normal(5, 90, 1000)
sample2= np.random.normal(5, 95, 1000)
sample3= np.random.normal(5, 100, 1000)
sample4= np.random.normal(5, 95, 1000)
sample= list([sample1, sample2, sample3, sample4])


fig, ax = plt.subplots()


# build a violin plot
ax.violinplot(sample, showmeans=False, showmedians=True)


# add title and axis labels
ax.set_title('violin plot')
ax.set_xlabel('x-axis')
ax.set_ylabel('y-axis')


# add x-tick labels
xticklabels = ['sample 1', 'sample 2', 'sample 3', 'sample 4']
ax.set_xticks([1,2,3,4])
ax.set_xticklabels(xticklabels)


# add horizontal grid lines
ax.yaxis.grid(True)


# show the plot
plt.show()
Output
Output of example | insideAIML
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