Matplotlib: scrolling plot

Date:2010-01-03 (last modified), 2010-01-03 (created)

Controlling an Embedded Plot with wx Scrollbars¶

When plotting a very long sequence in a matplotlib canvas embedded in a wxPython application, it sometimes is useful to be able to display a portion of the sequence without resorting to a scrollable window so that both axes remain visible. Here is how to do so:

In [ ]:

from numpy import arange, sin, pi, float, size

import matplotlib
matplotlib.use('WXAgg')
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg
from matplotlib.figure import Figure

import wx

class MyFrame(wx.Frame):
    def __init__(self, parent, id):
        wx.Frame.__init__(self,parent, id, 'scrollable plot',
                style=wx.DEFAULT_FRAME_STYLE ^ wx.RESIZE_BORDER,
                size=(800, 400))
        self.panel = wx.Panel(self, -1)

        self.fig = Figure((5, 4), 75)
        self.canvas = FigureCanvasWxAgg(self.panel, -1, self.fig)
        self.scroll_range = 400
        self.canvas.SetScrollbar(wx.HORIZONTAL, 0, 5,
                                 self.scroll_range)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.canvas, -1, wx.EXPAND)

        self.panel.SetSizer(sizer)
        self.panel.Fit()

        self.init_data()
        self.init_plot()

        self.canvas.Bind(wx.EVT_SCROLLWIN, self.OnScrollEvt)

    def init_data(self):

        # Generate some data to plot:
        self.dt = 0.01
        self.t = arange(0,5,self.dt)
        self.x = sin(2*pi*self.t)

        # Extents of data sequence: 
        self.i_min = 0
        self.i_max = len(self.t)

        # Size of plot window:       
        self.i_window = 100

        # Indices of data interval to be plotted:
        self.i_start = 0
        self.i_end = self.i_start + self.i_window

    def init_plot(self):
        self.axes = self.fig.add_subplot(111)
        self.plot_data = \
                  self.axes.plot(self.t[self.i_start:self.i_end],
                                 self.x[self.i_start:self.i_end])[0]

    def draw_plot(self):

        # Update data in plot:
        self.plot_data.set_xdata(self.t[self.i_start:self.i_end])
        self.plot_data.set_ydata(self.x[self.i_start:self.i_end])

        # Adjust plot limits:
        self.axes.set_xlim((min(self.t[self.i_start:self.i_end]),
                           max(self.t[self.i_start:self.i_end])))
        self.axes.set_ylim((min(self.x[self.i_start:self.i_end]),
                            max(self.x[self.i_start:self.i_end])))

        # Redraw:                  
        self.canvas.draw()

    def OnScrollEvt(self, event):

     # Update the indices of the plot:
        self.i_start = self.i_min + event.GetPosition()
        self.i_end = self.i_min + self.i_window + event.GetPosition()
        self.draw_plot()

class MyApp(wx.App):
    def OnInit(self):
        self.frame = MyFrame(parent=None,id=-1)
        self.frame.Show()
        self.SetTopWindow(self.frame)
        return True

if __name__ == '__main__':
    app = MyApp()
    app.MainLoop()

Section author: LevGivon