I have some simple code (I've cut it down a lot, but kept the problem)
that tries to plot two sets of data using the same variables. It
appears that re-using the variables from the first plot for the second
plot affects the first plot. In fact the two plots become identical. I
am guessing that the variables used in the 1st plot are pointed to by
other matplotlib internal variables (but not plotted until Show() is
called -- a guess on my part). In Python fashion when I change a
variable in preparation for the 2nd plot, the values in the 1st plot
change, too.
Here is sample code based on some code sent to me by Jeremy O'Donoghue
as an example of how to embed matplotlib in wxPython. The problem is in
the method plot_data in the PlotFigure class. Note how x and y are
reused for the 2nd plot. The output should be an 'X' shape, but only
one line shows up, the 2nd plot line. If you add new variables to do
the 2nd plot (e.g. u=zeroes((2,),Float), v=zeroes((2,),Float)) and
replace the x and y in the 2nd plot with those variables, then it works
correctly.
Is this good matplotlib behavior? Is it necessary to use new variables
for each call of plot?
I am using wxPython wx-2.6-mac-unicode, matplotlib 0.82, Python 2.4,
on a Macintosh Powerbook G4, OS X 10.4
--------------------------------- The code (self contained as run from
BBEdit through the Terminal):
#!/usr/local/bin/pythonw
from Numeric import *
import matplotlib
matplotlib.use('WX')
from matplotlib.backends.backend_wx import Toolbar, FigureCanvasWx,\
FigureManager
from matplotlib.figure import Figure
from matplotlib.axes import Subplot
import matplotlib.numerix as numpy
import wx
class PlotFigure(wx.Frame):
def __init__(self):
wx.Frame.__init__(self, None, -1, "Test embedded wx.Figure")
self.fig = Figure((10,8), 75)
self.canvas = FigureCanvasWx(self, -1, self.fig)
self.toolbar = Toolbar(self.canvas)
self.toolbar.Realize()
# On Windows, default frame size behaviour is incorrect
# you don't need this under Linux
tw, th = self.toolbar.GetSizeTuple()
fw, fh = self.canvas.GetSizeTuple()
self.toolbar.SetSize(wx.Size(fw, th))
# Create a figure manager to manage things
self.figmgr = FigureManager(self.canvas, 1, self)
# Now put all into a sizer
sizer = wx.BoxSizer(wx.VERTICAL)
# This way of adding to sizer allows resizing
sizer.Add(self.canvas, 1, wx.LEFT|wx.TOP|wx.GROW)
# Best to allow the toolbar to resize!
sizer.Add(self.toolbar, 0, wx.GROW)
self.SetSizer(sizer)
self.Fit()
# *** HERE'S THE PROBLEM PART ***
def plot_data(self):
# Use ths line if using a toolbar
a = self.fig.add_subplot(111)
# Or this one if there is no toolbar
#a = Subplot(self.fig, 111)
x=zeros((2,),Float)
y=zeros((2,),Float)
# 1st Plot .................
x[0]= 1.0
y[0]= 1.0
x[1]=-1.0
y[1]=-1.0
a.plot(x,y)
# 2nd Plot .................
x[0]=-1.0
y[0]= 1.0
x[1]= 1.0
y[1]=-1.0
a.plot(x,y)
self.toolbar.update()
def GetToolBar(self):
# You will need to override GetToolBar if you are using an
# unmanaged toolbar in your frame
return self.toolbar
if __name__ == '__main__':
# Plot
app = wx.PySimpleApp(0)
frame = PlotFigure()
frame.plot_data()
frame.Show()
app.MainLoop()
--
Cheers,
Lou Pecora
Code 6362
Naval Research Lab
Washington, DC 20375
USA
Ph: +202-767-6002
email: pe...@an...