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

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

.. _sphx_glr_gallery_images_contours_and_fields_contourf_log.py:


============================
Contourf and log color scale
============================

Demonstrate use of a log color scale in contourf


.. code-block:: default


    import matplotlib.pyplot as plt
    import numpy as np
    from numpy import ma
    from matplotlib import ticker, cm

    N = 100
    x = np.linspace(-3.0, 3.0, N)
    y = np.linspace(-2.0, 2.0, N)

    X, Y = np.meshgrid(x, y)

    # A low hump with a spike coming out.
    # Needs to have z/colour axis on a log scale so we see both hump and spike.
    # linear scale only shows the spike.
    Z1 = np.exp(-(X)**2 - (Y)**2)
    Z2 = np.exp(-(X * 10)**2 - (Y * 10)**2)
    z = Z1 + 50 * Z2

    # Put in some negative values (lower left corner) to cause trouble with logs:
    z[:5, :5] = -1

    # The following is not strictly essential, but it will eliminate
    # a warning.  Comment it out to see the warning.
    z = ma.masked_where(z <= 0, z)


    # Automatic selection of levels works; setting the
    # log locator tells contourf to use a log scale:
    fig, ax = plt.subplots()
    cs = ax.contourf(X, Y, z, locator=ticker.LogLocator(), cmap=cm.PuBu_r)

    # Alternatively, you can manually set the levels
    # and the norm:
    # lev_exp = np.arange(np.floor(np.log10(z.min())-1),
    #                    np.ceil(np.log10(z.max())+1))
    # levs = np.power(10, lev_exp)
    # cs = ax.contourf(X, Y, z, levs, norm=colors.LogNorm())

    cbar = fig.colorbar(cs)

    plt.show()




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contourf_log_001.png
    :class: sphx-glr-single-img





------------

References
""""""""""

The use of the following functions, methods and classes is shown
in this example:


.. code-block:: default


    import matplotlib
    matplotlib.axes.Axes.contourf
    matplotlib.pyplot.contourf
    matplotlib.figure.Figure.colorbar
    matplotlib.pyplot.colorbar
    matplotlib.axes.Axes.legend
    matplotlib.pyplot.legend
    matplotlib.ticker.LogLocator








.. _sphx_glr_download_gallery_images_contours_and_fields_contourf_log.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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


.. only:: html

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

    Keywords: matplotlib code example, codex, python plot, pyplot
    `Gallery generated by Sphinx-Gallery
    <https://sphinx-gallery.readthedocs.io>`_