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

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

.. _sphx_glr_gallery_images_contours_and_fields_contour_demo.py:


============
Contour Demo
============

Illustrate simple contour plotting, contours on an image with
a colorbar for the contours, and labelled contours.

See also the :doc:`contour image example
</gallery/images_contours_and_fields/contour_image>`.



.. code-block:: python

    import matplotlib
    import numpy as np
    import matplotlib.cm as cm
    import matplotlib.pyplot as plt


    delta = 0.025
    x = np.arange(-3.0, 3.0, delta)
    y = np.arange(-2.0, 2.0, delta)
    X, Y = np.meshgrid(x, y)
    Z1 = np.exp(-X**2 - Y**2)
    Z2 = np.exp(-(X - 1)**2 - (Y - 1)**2)
    Z = (Z1 - Z2) * 2







Create a simple contour plot with labels using default colors.  The
inline argument to clabel will control whether the labels are draw
over the line segments of the contour, removing the lines beneath
the label



.. code-block:: python


    fig, ax = plt.subplots()
    CS = ax.contour(X, Y, Z)
    ax.clabel(CS, inline=1, fontsize=10)
    ax.set_title('Simplest default with labels')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_001.png
    :class: sphx-glr-single-img




contour labels can be placed manually by providing list of positions
(in data coordinate). See ginput_manual_clabel.py for interactive
placement.



.. code-block:: python


    fig, ax = plt.subplots()
    CS = ax.contour(X, Y, Z)
    manual_locations = [(-1, -1.4), (-0.62, -0.7), (-2, 0.5), (1.7, 1.2), (2.0, 1.4), (2.4, 1.7)]
    ax.clabel(CS, inline=1, fontsize=10, manual=manual_locations)
    ax.set_title('labels at selected locations')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_002.png
    :class: sphx-glr-single-img




You can force all the contours to be the same color.



.. code-block:: python


    fig, ax = plt.subplots()
    CS = ax.contour(X, Y, Z, 6,
                     colors='k',  # negative contours will be dashed by default
                     )
    ax.clabel(CS, fontsize=9, inline=1)
    ax.set_title('Single color - negative contours dashed')




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_003.png
    :class: sphx-glr-single-img




You can set negative contours to be solid instead of dashed:



.. code-block:: python


    matplotlib.rcParams['contour.negative_linestyle'] = 'solid'
    fig, ax = plt.subplots()
    CS = ax.contour(X, Y, Z, 6,
                     colors='k',  # negative contours will be dashed by default
                     )
    ax.clabel(CS, fontsize=9, inline=1)
    ax.set_title('Single color - negative contours solid')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_004.png
    :class: sphx-glr-single-img




And you can manually specify the colors of the contour



.. code-block:: python


    fig, ax = plt.subplots()
    CS = ax.contour(X, Y, Z, 6,
                     linewidths=np.arange(.5, 4, .5),
                     colors=('r', 'green', 'blue', (1, 1, 0), '#afeeee', '0.5')
                     )
    ax.clabel(CS, fontsize=9, inline=1)
    ax.set_title('Crazy lines')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_005.png
    :class: sphx-glr-single-img




Or you can use a colormap to specify the colors; the default
colormap will be used for the contour lines



.. code-block:: python


    fig, ax = plt.subplots()
    im = ax.imshow(Z, interpolation='bilinear', origin='lower',
                    cmap=cm.gray, extent=(-3, 3, -2, 2))
    levels = np.arange(-1.2, 1.6, 0.2)
    CS = ax.contour(Z, levels, origin='lower', cmap='flag',
                    linewidths=2, extent=(-3, 3, -2, 2))

    # Thicken the zero contour.
    zc = CS.collections[6]
    plt.setp(zc, linewidth=4)

    ax.clabel(CS, levels[1::2],  # label every second level
              inline=1, fmt='%1.1f',
              cmap='flag', fontsize=14)

    # make a colorbar for the contour lines
    CB = fig.colorbar(CS, shrink=0.8, extend='both')

    ax.set_title('Lines with colorbar')

    # We can still add a colorbar for the image, too.
    CBI = fig.colorbar(im, orientation='horizontal', shrink=0.8)

    # This makes the original colorbar look a bit out of place,
    # so let's improve its position.

    l, b, w, h = ax.get_position().bounds
    ll, bb, ww, hh = CB.ax.get_position().bounds
    CB.ax.set_position([ll, b + 0.1*h, ww, h*0.8])

    plt.show()




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_contour_demo_006.png
    :class: sphx-glr-single-img




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

References
""""""""""

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



.. code-block:: python


    import matplotlib
    matplotlib.axes.Axes.contour
    matplotlib.pyplot.contour
    matplotlib.figure.Figure.colorbar
    matplotlib.pyplot.colorbar
    matplotlib.axes.Axes.clabel
    matplotlib.pyplot.clabel
    matplotlib.axes.Axes.set_position
    matplotlib.axes.Axes.get_position







.. _sphx_glr_download_gallery_images_contours_and_fields_contour_demo.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: contour_demo.ipynb <contour_demo.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>`_
