

.. _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


    plt.figure()
    plt.gca().set_aspect('equal')
    plt.tripcolor(triang, z, shading='flat')
    plt.colorbar()
    plt.title('tripcolor of Delaunay triangulation, flat shading')




.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_001.png
    :align: center




Illustrate Gouraud shading.



.. code-block:: python


    plt.figure()
    plt.gca().set_aspect('equal')
    plt.tripcolor(triang, z, shading='gouraud')
    plt.colorbar()
    plt.title('tripcolor of Delaunay triangulation, gouraud shading')





.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_002.png
    :align: center




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


    plt.figure()
    plt.gca().set_aspect('equal')
    plt.tripcolor(x, y, triangles, facecolors=zfaces, edgecolors='k')
    plt.colorbar()
    plt.title('tripcolor of user-specified triangulation')
    plt.xlabel('Longitude (degrees)')
    plt.ylabel('Latitude (degrees)')

    plt.show()



.. image:: /gallery/images_contours_and_fields/images/sphx_glr_tripcolor_demo_003.png
    :align: center




**Total running time of the script:** ( 0 minutes  0.355 seconds)



.. only :: html

 .. container:: sphx-glr-footer


  .. 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

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