cursor_demo.py

#!/usr/bin/env python
# -*- 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
"""
from __future__ import print_function
from pylab import *


class Cursor:
    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) )
        draw()


class SnaptoCursor:
    """
    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 = 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))
        draw()

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

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

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