title: Graphs not updating (matplotlib)
body: <p>I'm trying to make a GUI that contains several figures, each with an axes (is 'axes' plural?). I managed to get the leftmost graph to plot upon initializing the respective widget using this line:</p>
  
  <pre><code>    self.leftImage = self.leftPlot.axes.imshow(self.defaultSlide, cmap = self.mymap)
  </code></pre>
  
  <p>where <code>self.leftPlot</code> contains the necessary figure properties. I noticed that I didn't have to call <code>plt.show()</code> or its variants for this part, which I don't know whether it's significant or not.</p>
  
  <p>Later in the code, I called <code>self.leftImage.set_data(newSlide)</code>, but nothing seems to change even though it definitely gets executed. I tried setting leftImage to a new instance of <code>imshow()</code>, but that doesn't seem to fix anything.</p>
  
  <p>My imports:</p>
  
  <pre><code>from PySide import QtCore, QtGui
  from PySide.QtCore import *
  from PySide.QtGui import *
  import matplotlib
  
  matplotlib.use('Qt4Agg')
  matplotlib.rcParams['backend.qt4']='PySide'
  
  from matplotlib.figure import Figure
  from matplotlib.backends.backend_qt4agg import FigureCanvasQTAgg as FigureCanvas
  from matplotlib.backends.backend_qt4agg import NavigationToolbar2QTAgg as NavigationToolbar
  import matplotlib.pyplot as plt
  </code></pre>
  
  <p>I'm fairly new to matplotlib, but I do come from a MATLAB background if that helps.</p>