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
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 = min(np.searchsorted(self.x, [x])[0], len(self.x) - 1)
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()
Total running time of the script: ( 0 minutes 0.000 seconds)