Span Selector#

The SpanSelector is a mouse widget that enables selecting a range on an axis.

Here, an x-range can be selected on the upper axis; a detailed view of the selected range is then plotted on the lower axis.


If the SpanSelector object is garbage collected you will lose the interactivity. You must keep a hard reference to it to prevent this.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import SpanSelector

# Fixing random state for reproducibility

fig, (ax1, ax2) = plt.subplots(2, figsize=(8, 6))

x = np.arange(0.0, 5.0, 0.01)
y = np.sin(2 * np.pi * x) + 0.5 * np.random.randn(len(x))

ax1.plot(x, y)
ax1.set_ylim(-2, 2)
ax1.set_title('Press left mouse button and drag '
              'to select a region in the top graph')

line2, = ax2.plot([], [])

def onselect(xmin, xmax):
    indmin, indmax = np.searchsorted(x, (xmin, xmax))
    indmax = min(len(x) - 1, indmax)

    region_x = x[indmin:indmax]
    region_y = y[indmin:indmax]

    if len(region_x) >= 2:
        line2.set_data(region_x, region_y)
        ax2.set_xlim(region_x[0], region_x[-1])
        ax2.set_ylim(region_y.min(), region_y.max())

span = SpanSelector(
    props=dict(alpha=0.5, facecolor="tab:blue"),
# Set useblit=True on most backends for enhanced performance.
Press left mouse button and drag to select a region in the top graph


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

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