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"""
=============
Looking glass
=============
Example using mouse events to simulate a looking glass for inspecting data.
.. 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
import matplotlib.patches as patches
# Fixing random state for reproducibility
np.random.seed(19680801)
x, y = np.random.rand(2, 200)
fig, ax = plt.subplots()
circ = patches.Circle((0.5, 0.5), 0.25, alpha=0.8, fc='yellow')
ax.add_patch(circ)
ax.plot(x, y, alpha=0.2)
line, = ax.plot(x, y, alpha=1.0, clip_path=circ)
ax.set_title("Left click and drag to move looking glass")
class EventHandler:
def __init__(self):
fig.canvas.mpl_connect('button_press_event', self.on_press)
fig.canvas.mpl_connect('button_release_event', self.on_release)
fig.canvas.mpl_connect('motion_notify_event', self.on_move)
self.x0, self.y0 = circ.center
self.pressevent = None
def on_press(self, event):
if event.inaxes != ax:
return
if not circ.contains(event)[0]:
return
self.pressevent = event
def on_release(self, event):
self.pressevent = None
self.x0, self.y0 = circ.center
def on_move(self, event):
if self.pressevent is None or event.inaxes != self.pressevent.inaxes:
return
dx = event.xdata - self.pressevent.xdata
dy = event.ydata - self.pressevent.ydata
circ.center = self.x0 + dx, self.y0 + dy
line.set_clip_path(circ)
fig.canvas.draw()
handler = EventHandler()
plt.show()
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