CODEWITHSUNDEEP
pythonmatplotlibwxpython
miik
miik

Reputation: 663

selecting points from a graph matplotlib

At the moment I have a scatter graph which I can zoom in, move around etc.
What I also want to do is be able to select a certain number of points on the graph, then store the selected points in an array.
Is there any special function in matplotlib I can use?
Any help will 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()

Upvotes: 4

Views: 6438

Answers (1)

crayzeewulf
crayzeewulf

Reputation: 6010

The code below provides a possible solution. The basic method may be summarized as follows:

  • One attaches a handler for pick_event that keeps appending the picked data indices to a list self._picked_indices.
  • A key_press_event handler clears the self._picked_indices list whenever the user presses the escape key.
  • The method MyFrame.picked_points returns a list of coordinates of currently selected points. This method returns None if no points have been selected yet (you can modify it to return an empty list in this case if that is more convenient).

This way you can keep selecting points by clicking on them. But if you want to start over again, just press escape and start picking 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()

Upvotes: 2

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