for i in nm.arange(len(self.dummyy)):
    if self.dummyy[i] < self.y1:
        self.dummyy[i] = nm.NaN
else:
    pass
for i in nm.arange(len(self.dummyz)):
    if self.dummyz[i] < self.z1:
        self.dummyz[i] = nm.NaN
else:
    pass
controlset.a.plot(self.dummyx, self.dummyy, self.dummyz)
self.a.set_xlim3d(self.x1, self.x2)
self.a.set_ylim3d(self.y1, self.y2)
self.a.set_zlim3d(self.z1, self.z2)
set_xlim,set_ylim,set_zlim commands in matplotlib fail to clip displayed data