Matplotlib: Label points on mouseover

Question

I have a scatter plot with several thousand points. This post tells me how to label them:

Matplotlib: How to put individual tags for a scatter plot

But that will look like a disaster with so many points. What I would like instead is to have a "tool tip" type label that pops up when you mouseover a point. Is that possible using matplotlib?

Answer 1

Once you get the coords of the point you can show them or any object-linked info in a textctrl in the toolbar. For this you have to instantiate a toolbar (NavigationToolbar2Wx()) in your canvas and add the textcontrol there. This is not as nice as a popup but it does the job.

Here you have an example of customizing your toolbar (only showing the x coordinate in the txtctrl):

#!/usr/bin/env python
#-*- coding: utf-8 -*-
#
"""
jvisor_spectrum_panel (visor_07)
25 julio 2010
"""
#
import wx
from matplotlib.figure import Figure
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas
from matplotlib.backends.backend_wx import NavigationToolbar2Wx
#
#
class SpectrumPanel(wx.Panel):
    def __init__(self, parent, xlabel='m/z', ylabel='Intensity'):
        wx.Panel.__init__(self, parent)
        #
        self.parent = parent
        self.xlabel = xlabel
        self.ylabel = ylabel
        self.SetBackgroundColour("white")
        #
        self.figure = Figure()
        self.canvas = FigureCanvas(self, -1, self.figure)
        #
        self.add_toolbar()
        #
        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.canvas, 1, wx.LEFT | wx.TOP| wx.GROW| wx.EXPAND)
        sizer.Add(self.toolbar, 0, wx.LEFT)
        self.canvas.mpl_connect('motion_notify_event', self.on_motion)
        self.SetSizer(sizer)
        self.Fit()
        self.clean()
    #
    def add_toolbar(self):
        ""
        self.toolbar = NavigationToolbar2Wx(self.canvas)

        mass_txt = wx.StaticText(self.toolbar, label='m/z', pos=(230, 7),
                                                             size=(25, 17))
        mass_txt.SetBackgroundColour("light gray")
        self.mass = wx.TextCtrl(self.toolbar, pos=(260,4), size=(50, 22),
                                                           style=wx.TE_READONLY)
        #
        self.toolbar.SetToolBitmapSize(wx.Size(24, 25))
        self.toolbar.SetMinSize((1500, 31))
        self.toolbar.Realize()
        self.toolbar.Update()
    #
    def clean(self):
        ""
        self.figure.clear()
        self.axes = self.figure.add_subplot(111)
    #
    def dibuja(self):
        "dibuja el canvas"
        self.axes.set_xlabel(self.xlabel) 
        self.axes.set_ylabel(self.ylabel)
        self.canvas.draw()
    #
    def on_motion(self, evt):
        if evt.inaxes:
            xpos = evt.xdata
            self.mass.SetValue(' %0.1f' % (xpos))


if __name__ == '__main__':
    ""
    class TestFrame(wx.Frame):
        def __init__(self, *args, **kargs):
            wx.Frame.__init__(self, *args, **kargs)
            self.panel = SpectrumPanel(self)
            self.Fit()
    #        
    app = wx.PySimpleApp()
    fr = TestFrame(None)
    fr.Show()
    app.MainLoop()

And here you can see the new control in the toolbar: