pyQt Matplotlib widget live data updates

Question

Writing in Python 2.7 using pyQt 4.8.5:

How may I update a Matplotlib widget in real time within pyQt? Currently I'm sampling data (random.gauss for now), appending this and plotting - you can see that I'm clearing the figure each time and re-plotting for each call:

def getData(self):
    self.data = random.gauss(10,0.1)
    self.ValueTotal.append(self.data)
    self.updateData()

def updateData(self):
    self.ui.graph.axes.clear()
    self.ui.graph.axes.hold(True)
    self.ui.graph.axes.plot(self.ValueTotal,'r-')
    self.ui.graph.axes.grid()
    self.ui.graph.draw()

My GUI works though I think this is the wrong way to achieve this as its highly inefficient, I believe I should use the 'animate call'(?) whilst plotting, though I don't know how.

Answer 1

One idea would be to update only the graphics object after the first plot was done. axes.plot should return a Line2D object whose x and y-data you can modify:

http://matplotlib.org/api/artist_api.html#matplotlib.lines.Line2D.set_xdata

So, once you have the line plotted, don't delete and plot a new one, but modify the existing:

def updateData(self):
    if not hasattr(self, 'line'):
        # this should only be executed on the first call to updateData
        self.ui.graph.axes.clear()
        self.ui.graph.axes.hold(True)
        self.line = self.ui.graph.axes.plot(self.ValueTotal,'r-')
        self.ui.graph.axes.grid()
    else:
        # now we only modify the plotted line
        self.line.set_xdata(np.arange(len(self.ValueTotal))
        self.line.set_ydata(self.ValueTotal)
    self.ui.graph.draw()