How to clear a matplotlib graph in PyQt

Hello everyone,

I Have a problem. I have a graph inserted in a PyQt interface and I
want to clear it (When I click on a button).

I initialise the graph like that:

class Graph(FigureCanvas):
    def __init__(self,parent):

        self.fig = Figure()
        self.ax = self.fig.add_subplot(111)
        FigureCanvas.__init__(self, self.fig)

        self.R1, time,= [], []

        self.l_R1, = self.ax.plot([], self.R1,"-o", color = 'b',
label='R1')

        self.fig.canvas.draw()
        FigureCanvas.updateGeometry(self)

Later on the program I append values to the arrays: self.R1 and time and I do:

self.l_R1.set_data(time, self.R1)
self.fig.canvas.draw()
FigureCanvas.updateGeometry(self)

So the values are correctly added to the Graph. My problem is I want
to clear the graph and re-initialize the arrays self.R1 and time to
empty arrays.
I've tried to create a def activated by a button that do:

        self.R1, time,= [], []

        self.l_R1, = self.ax.plot([], self.R1,"-o", color = 'b',
label='R1')

        self.fig.canvas.draw()
        FigureCanvas.updateGeometry(self)

But no effects...

Anybody has an idea?

Thanks!

Fab