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Travis-CI:

# pylab_examples example code: cursor_demo.pyΒΆ

```# -*- noplot -*-

"""
This example shows how to use matplotlib to provide a data cursor.  It
uses matplotlib to draw the cursor and may be a slow since this
requires redrawing the figure with every mouse move.

Faster cursoring is possible using native GUI drawing, as in
wxcursor_demo.py.

The mpldatacursor and mplcursors third-party packages can be used to achieve a
similar effect.  See
https://github.com/joferkington/mpldatacursor
https://github.com/anntzer/mplcursors
"""
from __future__ import print_function
import matplotlib.pyplot as plt
import numpy as np

class Cursor(object):
def __init__(self, ax):
self.ax = ax
self.lx = ax.axhline(color='k')  # the horiz line
self.ly = ax.axvline(color='k')  # the vert line

# text location in axes coords
self.txt = ax.text(0.7, 0.9, '', transform=ax.transAxes)

def mouse_move(self, event):
if not event.inaxes:
return

x, y = event.xdata, event.ydata
# update the line positions
self.lx.set_ydata(y)
self.ly.set_xdata(x)

self.txt.set_text('x=%1.2f, y=%1.2f' % (x, y))
plt.draw()

class SnaptoCursor(object):
"""
Like Cursor but the crosshair snaps to the nearest x,y point
For simplicity, I'm assuming x is sorted
"""

def __init__(self, ax, x, y):
self.ax = ax
self.lx = ax.axhline(color='k')  # the horiz line
self.ly = ax.axvline(color='k')  # the vert line
self.x = x
self.y = y
# text location in axes coords
self.txt = ax.text(0.7, 0.9, '', transform=ax.transAxes)

def mouse_move(self, event):

if not event.inaxes:
return

x, y = event.xdata, event.ydata

indx = np.searchsorted(self.x, [x])[0]
x = self.x[indx]
y = self.y[indx]
# update the line positions
self.lx.set_ydata(y)
self.ly.set_xdata(x)

self.txt.set_text('x=%1.2f, y=%1.2f' % (x, y))
print('x=%1.2f, y=%1.2f' % (x, y))
plt.draw()

t = np.arange(0.0, 1.0, 0.01)
s = np.sin(2*2*np.pi*t)
fig, ax = plt.subplots()

#cursor = Cursor(ax)
cursor = SnaptoCursor(ax, t, s)
plt.connect('motion_notify_event', cursor.mouse_move)

ax.plot(t, s, 'o')
plt.axis([0, 1, -1, 1])
plt.show()
```

Keywords: python, matplotlib, pylab, example, codex (see Search examples)