from __future__ import division
from pylab import *
def function(t):
u = lambda t: 1 if t >=0 else 0
return t**2*u(t) - t**2*u(t-1) + (t-2)**2*u(t-1) - u(t-3)
n, a = 1000, 4
T, y = arange(-a, a, a/n), []
for t in T:
y.append(function(t))
plot(T, y)
grid(True)
show()