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"""
==========
Lasso Demo
==========
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.
.. note::
This example exercises the interactive capabilities of Matplotlib, and this
will not appear in the static documentation. Please run this code on your
machine to see the interactivity.
You can copy and paste individual parts, or download the entire example
using the link at the bottom of the page.
"""
import matplotlib.pyplot as plt
import numpy as np
from matplotlib import colors as mcolors
from matplotlib import path
from matplotlib.collections import RegularPolyCollection
from matplotlib.widgets import Lasso
class LassoManager:
def __init__(self, ax, data):
# The information of whether a point has been selected or not is stored in the
# collection's array (0 = out, 1 = in), which then gets colormapped to blue
# (out) and red (in).
self.collection = RegularPolyCollection(
6, sizes=(100,), offset_transform=ax.transData,
offsets=data, array=np.zeros(len(data)),
clim=(0, 1), cmap=mcolors.ListedColormap(["tab:blue", "tab:red"]))
ax.add_collection(self.collection)
canvas = ax.figure.canvas
canvas.mpl_connect('button_press_event', self.on_press)
canvas.mpl_connect('button_release_event', self.on_release)
def callback(self, verts):
data = self.collection.get_offsets()
self.collection.set_array(path.Path(verts).contains_points(data))
canvas = self.collection.figure.canvas
canvas.draw_idle()
del self.lasso
def on_press(self, event):
canvas = self.collection.figure.canvas
if event.inaxes is not self.collection.axes or canvas.widgetlock.locked():
return
self.lasso = Lasso(event.inaxes, (event.xdata, event.ydata), self.callback)
canvas.widgetlock(self.lasso) # acquire a lock on the widget drawing
def on_release(self, event):
canvas = self.collection.figure.canvas
if hasattr(self, 'lasso') and canvas.widgetlock.isowner(self.lasso):
canvas.widgetlock.release(self.lasso)
if __name__ == '__main__':
np.random.seed(19680801)
ax = plt.figure().add_subplot(
xlim=(0, 1), ylim=(0, 1), title='Lasso points using left mouse button')
manager = LassoManager(ax, np.random.rand(100, 2))
plt.show()
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