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Version 2.2.2.post1772+gd9240e24b
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Lasso DemoΒΆ

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.

../../_images/sphx_glr_lasso_demo_001.png
from matplotlib import colors as mcolors, path
from matplotlib.collections import RegularPolyCollection
import matplotlib.pyplot as plt
from matplotlib.widgets import Lasso
import numpy as np


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__':

    np.random.seed(19680801)

    data = [Datum(*xy) for xy in np.random.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()

Keywords: matplotlib code example, codex, python plot, pyplot Gallery generated by Sphinx-Gallery