Initial commit.
#!/usr/bin/python
## 4.11
import scipy as sp
from scipy import signal
num = sp.array([11,-15,6])
den = signal.convolve([1,-2],signal.convolve([1,-1],[1,-1]))
u = sp.zeros(5)
u[0] = 1
y = signal.lfilter(num,den,u)
print num, den
#Plot of impulse response???