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

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

.. _sphx_glr_gallery_images_contours_and_fields_tripcolor_demo.py:


==============
Tripcolor Demo
==============

Pseudocolor plots of unstructured triangular grids.



.. code-block:: python

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







Creating a Triangulation without specifying the triangles results in the
Delaunay triangulation of the points.



.. code-block:: python


    # First create the x and y coordinates of the points.
    n_angles = 36
    n_radii = 8
    min_radius = 0.25
    radii = np.linspace(min_radius, 0.95, n_radii)

    angles = np.linspace(0, 2 * np.pi, n_angles, endpoint=False)
    angles = np.repeat(angles[..., np.newaxis], n_radii, axis=1)
    angles[:, 1::2] += np.pi / n_angles

    x = (radii * np.cos(angles)).flatten()
    y = (radii * np.sin(angles)).flatten()
    z = (np.cos(radii) * np.cos(3 * angles)).flatten()

    # Create the Triangulation; no triangles so Delaunay triangulation created.
    triang = tri.Triangulation(x, y)

    # Mask off unwanted triangles.
    triang.set_mask(np.hypot(x[triang.triangles].mean(axis=1),
                             y[triang.triangles].mean(axis=1))
                    < min_radius)







tripcolor plot.



.. code-block:: python


    fig1, ax1 = plt.subplots()
    ax1.set_aspect('equal')
    tpc = ax1.tripcolor(triang, z, shading='flat')
    fig1.colorbar(tpc)
    ax1.set_title('tripcolor of Delaunay triangulation, flat shading')




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_001.png
    :class: sphx-glr-single-img




Illustrate Gouraud shading.



.. code-block:: python


    fig2, ax2 = plt.subplots()
    ax2.set_aspect('equal')
    tpc = ax2.tripcolor(triang, z, shading='gouraud')
    fig2.colorbar(tpc)
    ax2.set_title('tripcolor of Delaunay triangulation, gouraud shading')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_002.png
    :class: sphx-glr-single-img




You can specify your own triangulation rather than perform a Delaunay
triangulation of the points, where each triangle is given by the indices of
the three points that make up the triangle, ordered in either a clockwise or
anticlockwise manner.



.. code-block:: python


    xy = np.asarray([
        [-0.101, 0.872], [-0.080, 0.883], [-0.069, 0.888], [-0.054, 0.890],
        [-0.045, 0.897], [-0.057, 0.895], [-0.073, 0.900], [-0.087, 0.898],
        [-0.090, 0.904], [-0.069, 0.907], [-0.069, 0.921], [-0.080, 0.919],
        [-0.073, 0.928], [-0.052, 0.930], [-0.048, 0.942], [-0.062, 0.949],
        [-0.054, 0.958], [-0.069, 0.954], [-0.087, 0.952], [-0.087, 0.959],
        [-0.080, 0.966], [-0.085, 0.973], [-0.087, 0.965], [-0.097, 0.965],
        [-0.097, 0.975], [-0.092, 0.984], [-0.101, 0.980], [-0.108, 0.980],
        [-0.104, 0.987], [-0.102, 0.993], [-0.115, 1.001], [-0.099, 0.996],
        [-0.101, 1.007], [-0.090, 1.010], [-0.087, 1.021], [-0.069, 1.021],
        [-0.052, 1.022], [-0.052, 1.017], [-0.069, 1.010], [-0.064, 1.005],
        [-0.048, 1.005], [-0.031, 1.005], [-0.031, 0.996], [-0.040, 0.987],
        [-0.045, 0.980], [-0.052, 0.975], [-0.040, 0.973], [-0.026, 0.968],
        [-0.020, 0.954], [-0.006, 0.947], [ 0.003, 0.935], [ 0.006, 0.926],
        [ 0.005, 0.921], [ 0.022, 0.923], [ 0.033, 0.912], [ 0.029, 0.905],
        [ 0.017, 0.900], [ 0.012, 0.895], [ 0.027, 0.893], [ 0.019, 0.886],
        [ 0.001, 0.883], [-0.012, 0.884], [-0.029, 0.883], [-0.038, 0.879],
        [-0.057, 0.881], [-0.062, 0.876], [-0.078, 0.876], [-0.087, 0.872],
        [-0.030, 0.907], [-0.007, 0.905], [-0.057, 0.916], [-0.025, 0.933],
        [-0.077, 0.990], [-0.059, 0.993]])
    x, y = np.rad2deg(xy).T

    triangles = np.asarray([
        [67, 66,  1], [65,  2, 66], [ 1, 66,  2], [64,  2, 65], [63,  3, 64],
        [60, 59, 57], [ 2, 64,  3], [ 3, 63,  4], [ 0, 67,  1], [62,  4, 63],
        [57, 59, 56], [59, 58, 56], [61, 60, 69], [57, 69, 60], [ 4, 62, 68],
        [ 6,  5,  9], [61, 68, 62], [69, 68, 61], [ 9,  5, 70], [ 6,  8,  7],
        [ 4, 70,  5], [ 8,  6,  9], [56, 69, 57], [69, 56, 52], [70, 10,  9],
        [54, 53, 55], [56, 55, 53], [68, 70,  4], [52, 56, 53], [11, 10, 12],
        [69, 71, 68], [68, 13, 70], [10, 70, 13], [51, 50, 52], [13, 68, 71],
        [52, 71, 69], [12, 10, 13], [71, 52, 50], [71, 14, 13], [50, 49, 71],
        [49, 48, 71], [14, 16, 15], [14, 71, 48], [17, 19, 18], [17, 20, 19],
        [48, 16, 14], [48, 47, 16], [47, 46, 16], [16, 46, 45], [23, 22, 24],
        [21, 24, 22], [17, 16, 45], [20, 17, 45], [21, 25, 24], [27, 26, 28],
        [20, 72, 21], [25, 21, 72], [45, 72, 20], [25, 28, 26], [44, 73, 45],
        [72, 45, 73], [28, 25, 29], [29, 25, 31], [43, 73, 44], [73, 43, 40],
        [72, 73, 39], [72, 31, 25], [42, 40, 43], [31, 30, 29], [39, 73, 40],
        [42, 41, 40], [72, 33, 31], [32, 31, 33], [39, 38, 72], [33, 72, 38],
        [33, 38, 34], [37, 35, 38], [34, 38, 35], [35, 37, 36]])

    xmid = x[triangles].mean(axis=1)
    ymid = y[triangles].mean(axis=1)
    x0 = -5
    y0 = 52
    zfaces = np.exp(-0.01 * ((xmid - x0) * (xmid - x0) +
                             (ymid - y0) * (ymid - y0)))







Rather than create a Triangulation object, can simply pass x, y and triangles
arrays to tripcolor directly.  It would be better to use a Triangulation
object if the same triangulation was to be used more than once to save
duplicated calculations.
Can specify one color value per face rather than one per point by using the
facecolors kwarg.



.. code-block:: python


    fig3, ax3 = plt.subplots()
    ax3.set_aspect('equal')
    tpc = ax3.tripcolor(x, y, triangles, facecolors=zfaces, edgecolors='k')
    fig3.colorbar(tpc)
    ax3.set_title('tripcolor of user-specified triangulation')
    ax3.set_xlabel('Longitude (degrees)')
    ax3.set_ylabel('Latitude (degrees)')

    plt.show()




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_003.png
    :class: sphx-glr-single-img




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

References
""""""""""

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



.. code-block:: python


    import matplotlib
    matplotlib.axes.Axes.tripcolor
    matplotlib.pyplot.tripcolor
    matplotlib.tri
    matplotlib.tri.Triangulation







.. _sphx_glr_download_gallery_images_contours_and_fields_tripcolor_demo.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: tripcolor_demo.ipynb <tripcolor_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>`_
