.. note::
    :class: sphx-glr-download-link-note

    Click :ref:`here <sphx_glr_download_gallery_images_contours_and_fields_quadmesh_demo.py>` to download the full example code
.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_images_contours_and_fields_quadmesh_demo.py:


=============
QuadMesh Demo
=============

pcolormesh uses a QuadMesh, a faster generalization of pcolor, but
with some restrictions.

This demo illustrates a bug in quadmesh with masked data.




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_quadmesh_demo_001.png
    :class: sphx-glr-single-img





.. code-block:: python


    import copy

    from matplotlib import cm, colors, pyplot as plt
    import numpy as np

    n = 12
    x = np.linspace(-1.5, 1.5, n)
    y = np.linspace(-1.5, 1.5, n * 2)
    X, Y = np.meshgrid(x, y)
    Qx = np.cos(Y) - np.cos(X)
    Qz = np.sin(Y) + np.sin(X)
    Z = np.sqrt(X**2 + Y**2) / 5
    Z = (Z - Z.min()) / (Z.max() - Z.min())

    # The color array can include masked values.
    Zm = np.ma.masked_where(np.abs(Qz) < 0.5 * np.max(Qz), Z)

    fig, axs = plt.subplots(1, 3)
    axs[0].pcolormesh(Qx, Qz, Z, shading='gouraud')
    axs[0].set_title('Without masked values')

    # You can control the color of the masked region.  We copy the default colormap
    # before modifying it.
    cmap = copy.copy(cm.get_cmap(plt.rcParams['image.cmap']))
    cmap.set_bad('y', 1.0)
    axs[1].pcolormesh(Qx, Qz, Zm, shading='gouraud', cmap=cmap)
    axs[1].set_title('With masked values')

    # Or use the default, which is transparent.
    axs[2].pcolormesh(Qx, Qz, Zm, shading='gouraud')
    axs[2].set_title('With masked values')

    fig.tight_layout()

    plt.show()


.. _sphx_glr_download_gallery_images_contours_and_fields_quadmesh_demo.py:


.. only :: html

 .. container:: sphx-glr-footer
    :class: sphx-glr-footer-example



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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


.. only:: html

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

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