.. _pylab_examples-cursor_demo:

pylab_examples example code: cursor_demo.py
===========================================

[`source code <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)
    ax = subplot(111)
    
    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()
    
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)