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# Cursor Demo

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 = 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)

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