.. _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
    :align: center





.. code-block:: python


    import numpy as np
    from matplotlib.pyplot import figure, show, savefig
    from matplotlib import cm, colors
    from numpy import ma

    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)
    Qx = (Qx + 1.1)
    Z = np.sqrt(X**2 + Y**2) / 5
    Z = (Z - Z.min()) / (Z.max() - Z.min())

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

    fig = figure()
    ax = fig.add_subplot(121)
    ax.pcolormesh(Qx, Qz, Z, shading='gouraud')
    ax.set_title('Without masked values')

    ax = fig.add_subplot(122)
    #  You can control the color of the masked region:
    # cmap = cm.RdBu
    # cmap.set_bad('y', 1.0)
    # ax.pcolormesh(Qx, Qz, Zm, cmap=cmap)
    #  Or use the default, which is transparent:
    col = ax.pcolormesh(Qx, Qz, Zm, shading='gouraud')
    ax.set_title('With masked values')


    show()

**Total running time of the script:** ( 0 minutes  0.036 seconds)



.. only :: html

 .. container:: sphx-glr-footer


  .. 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>`_