

.. _sphx_glr_gallery_pie_and_polar_charts_nested_pie.py:


=================
Nested pie charts
=================

The following examples show two ways to build a nested pie chart
in Matplotlib.




.. code-block:: python


    from matplotlib import pyplot as plt
    import numpy as np







The most straightforward way to build a pie chart is to use the
:meth:`pie method <matplotlib.axes.Axes.pie>`

In this case, pie takes values corresponding to counts in a group.
We'll first generate some fake data, corresponding to three groups.
In the outer circle, we'll treat each number as belonging to its
own group. In the inner circle, we'll plot them as members of their
original 3 groups.



.. code-block:: python


    vals = np.array([[1, 2, 3, 4], [2, 3, 4, 5], [3, 4, 5, 6]])
    fig, ax = plt.subplots()
    ax.pie(vals.flatten(), radius=1.2,
           colors=plt.rcParams["axes.prop_cycle"].by_key()["color"][:vals.shape[1]])
    ax.pie(vals.sum(axis=1), radius=1)
    ax.set(aspect="equal", title='Pie plot with `ax.pie`')

    plt.show()




.. image:: /gallery/pie_and_polar_charts/images/sphx_glr_nested_pie_001.png
    :align: center




However, you can accomplish the same output by using a bar plot on
axes with a polar coordinate system. This may give more flexibility on
the exact design of the plot.

In this case, we need to map x-values of the bar chart onto radians of
a circle.



.. code-block:: python


    fig, ax = plt.subplots(subplot_kw=dict(polar=True))

    left_inner = np.arange(0.0, 2 * np.pi, 2 * np.pi / 6)
    left_middle = np.arange(0.0, 2 * np.pi, 2 * np.pi / 12)
    left_outer = np.arange(0.0, 2 * np.pi, 2 * np.pi / 9)

    ax.bar(left=left_inner,
           width=2 * np.pi / 6, bottom=0, color='C0',
           linewidth=2, edgecolor='w',
           height=np.zeros_like(left_inner) + 5)

    ax.bar(left=left_middle,
           width=2 * np.pi / 12, bottom=5, color='C1',
           linewidth=2, edgecolor='w',
           height=np.zeros_like(left_middle) + 2)

    ax.bar(left=left_outer,
           width=2 * np.pi / 9, bottom=7, color='C2',
           linewidth=2, edgecolor='w',
           height=np.zeros_like(left_outer) + 3)

    ax.set(title="Pie plot with `ax.bar` and polar coordinates")
    ax.set_axis_off()
    plt.show()



.. image:: /gallery/pie_and_polar_charts/images/sphx_glr_nested_pie_002.png
    :align: center




**Total running time of the script:** ( 0 minutes  0.138 seconds)



.. container:: sphx-glr-footer


  .. container:: sphx-glr-download

     :download:`Download Python source code: nested_pie.py <nested_pie.py>`



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: nested_pie.ipynb <nested_pie.ipynb>`

.. rst-class:: sphx-glr-signature

    `Generated by Sphinx-Gallery <https://sphinx-gallery.readthedocs.io>`_
