

.. _sphx_glr_gallery_event_handling_lasso_demo.py:


==========
Lasso Demo
==========

Show how to use a lasso to select a set of points and get the indices
of the selected points.  A callback is used to change the color of the
selected points

This is currently a proof-of-concept implementation (though it is
usable as is).  There will be some refinement of the API.




.. image:: /gallery/event_handling/images/sphx_glr_lasso_demo_001.png
    :align: center





.. code-block:: python

    from matplotlib.widgets import Lasso
    from matplotlib.collections import RegularPolyCollection
    from matplotlib import colors as mcolors, path

    import matplotlib.pyplot as plt
    from numpy import nonzero
    from numpy.random import rand


    class Datum(object):
        colorin = mcolors.to_rgba("red")
        colorout = mcolors.to_rgba("blue")

        def __init__(self, x, y, include=False):
            self.x = x
            self.y = y
            if include:
                self.color = self.colorin
            else:
                self.color = self.colorout


    class LassoManager(object):
        def __init__(self, ax, data):
            self.axes = ax
            self.canvas = ax.figure.canvas
            self.data = data

            self.Nxy = len(data)

            facecolors = [d.color for d in data]
            self.xys = [(d.x, d.y) for d in data]
            self.collection = RegularPolyCollection(
                6, sizes=(100,),
                facecolors=facecolors,
                offsets=self.xys,
                transOffset=ax.transData)

            ax.add_collection(self.collection)

            self.cid = self.canvas.mpl_connect('button_press_event', self.onpress)

        def callback(self, verts):
            facecolors = self.collection.get_facecolors()
            p = path.Path(verts)
            ind = p.contains_points(self.xys)
            for i in range(len(self.xys)):
                if ind[i]:
                    facecolors[i] = Datum.colorin
                else:
                    facecolors[i] = Datum.colorout

            self.canvas.draw_idle()
            self.canvas.widgetlock.release(self.lasso)
            del self.lasso

        def onpress(self, event):
            if self.canvas.widgetlock.locked():
                return
            if event.inaxes is None:
                return
            self.lasso = Lasso(event.inaxes,
                               (event.xdata, event.ydata),
                               self.callback)
            # acquire a lock on the widget drawing
            self.canvas.widgetlock(self.lasso)

    if __name__ == '__main__':

        data = [Datum(*xy) for xy in rand(100, 2)]
        ax = plt.axes(xlim=(0, 1), ylim=(0, 1), autoscale_on=False)
        ax.set_title('Lasso points using left mouse button')

        lman = LassoManager(ax, data)

        plt.show()

**Total running time of the script:** ( 0 minutes  0.034 seconds)



.. container:: sphx-glr-footer


  .. container:: sphx-glr-download

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



  .. container:: sphx-glr-download

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

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

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