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

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

.. _sphx_glr_gallery_event_handling_trifinder_event_demo.py:


====================
Trifinder Event Demo
====================

Example showing the use of a TriFinder object.  As the mouse is moved over the
triangulation, the triangle under the cursor is highlighted and the index of
the triangle is displayed in the plot title.




.. image:: /gallery/event_handling/images/sphx_glr_trifinder_event_demo_001.png
    :class: sphx-glr-single-img





.. code-block:: python

    import matplotlib.pyplot as plt
    from matplotlib.tri import Triangulation
    from matplotlib.patches import Polygon
    import numpy as np


    def update_polygon(tri):
        if tri == -1:
            points = [0, 0, 0]
        else:
            points = triang.triangles[tri]
        xs = triang.x[points]
        ys = triang.y[points]
        polygon.set_xy(np.column_stack([xs, ys]))


    def motion_notify(event):
        if event.inaxes is None:
            tri = -1
        else:
            tri = trifinder(event.xdata, event.ydata)
        update_polygon(tri)
        plt.title('In triangle %i' % tri)
        event.canvas.draw()


    # Create a Triangulation.
    n_angles = 16
    n_radii = 5
    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()
    triang = Triangulation(x, y)
    triang.set_mask(np.hypot(x[triang.triangles].mean(axis=1),
                             y[triang.triangles].mean(axis=1))
                    < min_radius)

    # Use the triangulation's default TriFinder object.
    trifinder = triang.get_trifinder()

    # Setup plot and callbacks.
    plt.subplot(111, aspect='equal')
    plt.triplot(triang, 'bo-')
    polygon = Polygon([[0, 0], [0, 0]], facecolor='y')  # dummy data for xs,ys
    update_polygon(-1)
    plt.gca().add_patch(polygon)
    plt.gcf().canvas.mpl_connect('motion_notify_event', motion_notify)
    plt.show()


.. _sphx_glr_download_gallery_event_handling_trifinder_event_demo.py:


.. only :: html

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



  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

     :download:`Download Jupyter notebook: trifinder_event_demo.ipynb <trifinder_event_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>`_