Selection of points from matplotlib chart

Question

At the moment I have a scatter plot that I can enlarge, move, etc.
What I also want to do is select a certain number of points on the chart, and then save the selected points in an array. Is there any special function in matplotlib that I can use?
Any help would be greatly appreciated.

My code

import os import wx import numpy as nump import matplotlib matplotlib.use('WXAgg') import matplotlib.figure as fg import matplotlib.backends.backend_wxagg as wxagg class MyFrame(wx.Frame): def __init__(self): wx.Frame.__init__(self, None, -1, 'Title') self.create_main_panel() self.draw_figure() def create_main_panel(self): self.panel = wx.Panel(self) self.dpi = 100 self.fig = fg.Figure((5.0, 4.0), dpi=self.dpi) self.canvas = wxagg.FigureCanvasWxAgg(self.panel, -1, self.fig) self.axes = self.fig.add_subplot(111) self.toolbar = wxagg.NavigationToolbar2WxAgg(self.canvas) self.vbox = wx.BoxSizer(wx.VERTICAL) self.vbox.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.GROW) self.vbox.AddSpacer(25) self.vbox.Add(self.toolbar, 0, wx.EXPAND) self.panel.SetSizer(self.vbox) self.vbox.Fit(self) def draw_figure(self): self.axes.clear() x, y = [2,3,4,5] self.axes.scatter(x, y) self.canvas.draw() def on_exit(self, event): self.Destroy() if __name__ == '__main__': app = wx.PySimpleApp() app.frame = MyFrame() app.frame.Show() app.MainLoop() 

Answer 1

The code below gives a possible solution. The main method can be summarized as follows:

• Attaches a handler for pick_event , which adds a list of selected data to the self._picked_indices list.
• The key_press_event handler clears the self._picked_indices list whenever the user presses the escape key.
• The MyFrame.picked_points method returns a list of coordinates of the currently selected points. This method returns None if no points have already been selected (you can change it to return an empty list in this case, if it is more convenient).

Thus, you can continue to select points by clicking on them. But if you want to start over, just hit escape and start the collection again.

 #! /usr/bin/env python import os import wx import numpy as nump import matplotlib matplotlib.use('WXAgg') import matplotlib.figure as fg import matplotlib.backends.backend_wxagg as wxagg class MyFrame(wx.Frame): def __init__(self): wx.Frame.__init__(self, None, -1, 'Title') self.create_main_panel() self.draw_figure() self._is_pick_started = False self._picked_indices = None def create_main_panel(self): self.panel = wx.Panel(self) self.dpi = 100 self.fig = fg.Figure((5.0, 4.0), dpi=self.dpi) self.canvas = wxagg.FigureCanvasWxAgg(self.panel, -1, self.fig) self.axes = self.fig.add_subplot(111) self.toolbar = wxagg.NavigationToolbar2WxAgg(self.canvas) self.vbox = wx.BoxSizer(wx.VERTICAL) self.vbox.Add(self.canvas, 1, wx.LEFT | wx.TOP | wx.GROW) self.vbox.AddSpacer(25) self.vbox.Add(self.toolbar, 0, wx.EXPAND) self.panel.SetSizer(self.vbox) self.vbox.Fit(self) self.fig.canvas.mpl_connect('pick_event', self.on_pick) self.fig.canvas.mpl_connect('key_press_event', self.on_key) def draw_figure(self): self.axes.clear() self._x_data, self._y_data = [[2,3], [4,5]] self.axes.scatter(self._x_data, self._y_data, picker=5) self.canvas.draw() def on_exit(self, event): self.Destroy() def picked_points(self): if self._picked_indices is None: return None else: return [ [self._x_data[i], self._y_data[i]] for i in self._picked_indices ] def on_pick(self, event): if not self._is_pick_started: self._picked_indices = [] self._is_pick_started = True for index in event.ind: if index not in self._picked_indices: self._picked_indices.append(index) print self.picked_points() def on_key(self, event): """If the user presses the Escape key then stop picking points and reset the list of picked points.""" if 'escape' == event.key: self._is_pick_started = False self._picked_indices = None return if __name__ == '__main__': app = wx.PySimpleApp() app.frame = MyFrame() app.frame.Show() app.MainLoop()