Rectangle and ellipse selectors#

Click somewhere, move the mouse, and release the mouse button. RectangleSelector and EllipseSelector draw a rectangle or an ellipse from the initial click position to the current mouse position (within the same axes) until the button is released. A connected callback receives the click- and release-events.

from matplotlib.widgets import EllipseSelector, RectangleSelector
import numpy as np
import matplotlib.pyplot as plt

def select_callback(eclick, erelease):
    Callback for line selection.

    *eclick* and *erelease* are the press and release events.
    x1, y1 = eclick.xdata, eclick.ydata
    x2, y2 = erelease.xdata, erelease.ydata
    print(f"({x1:3.2f}, {y1:3.2f}) --> ({x2:3.2f}, {y2:3.2f})")
    print(f"The buttons you used were: {eclick.button} {erelease.button}")

def toggle_selector(event):
    print('Key pressed.')
    if event.key == 't':
        for selector in selectors:
            name = type(selector).__name__
                print(f'{name} deactivated.')
                print(f'{name} activated.')

fig = plt.figure(constrained_layout=True)
axs = fig.subplots(2)

N = 100000  # If N is large one can see improvement by using blitting.
x = np.linspace(0, 10, N)

selectors = []
for ax, selector_class in zip(axs, [RectangleSelector, EllipseSelector]):
    ax.plot(x, np.sin(2*np.pi*x))  # plot something
    ax.set_title(f"Click and drag to draw a {selector_class.__name__}.")
        ax, select_callback,
        button=[1, 3],  # disable middle button
        minspanx=5, minspany=5,
    fig.canvas.mpl_connect('key_press_event', toggle_selector)
axs[0].set_title("Press 't' to toggle the selectors on and off.\n"
                 + axs[0].get_title())
Press 't' to toggle the selectors on and off. Click and drag to draw a RectangleSelector., Click and drag to draw a EllipseSelector.


The use of the following functions, methods, classes and modules is shown in this example:

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