'Add a new bar to our graph.'

def addBar(self, yval):

    percent = (yval / self.ymax)
    c = self.graph
    x0 = (self.xpos * self.barwidth)
    x1 = (x0 + self.barwidth)
    y0 = self.gheight
    y1 = ((1 - percent) * self.gheight)
    c.create_rectangle(x0, y0, x1, y1, fill='green')
    self.xpos += 1
    self.updateScrollRegions()
    self.graph.xview('moveto', '1.0')
