def zplane(self, a, b):
# Fix axes
ax = plt.gca()
ax.spines['left'].set_position('zero')
ax.spines['bottom'].set_position('zero')
ax.spines['right'].set_visible(False)
ax.spines['top'].set_visible(False)
# Draw circle
circle = patches.Circle((0, 0),
radius=1,
color='black',
ls='dashed',
fill=False)
ax.add_patch(circle)
# Make a and b of equal length
a = numpy.append(a, numpy.repeat(0, max(len(a), len(b)) - len(a)))
b = numpy.append(b, numpy.repeat(0, max(len(a), len(b)) - len(b)))
# Plot poles
p = numpy.roots(a)
plt.plot(p.real, p.imag, 'kx', ms=7)
# Plot zeros
z = numpy.roots(b)
plt.plot(z.real, z.imag, 'ko', ms=7)
plt.axis('scaled')
plt.show()
def stepz(self, signal_in, a, b):
step = numpy.repeat(0., len(signal_in))
step[numpy.where(signal_in >= 0)] = 1.
response = signal.lfilter(b, a, step)
return response
def impz(self, signal_in, a, b):
impulse = numpy.repeat(0., len(signal_in))
impulse[numpy.where(signal_in == 1)] = 1.
response = signal.lfilter(b, a, impulse)
return response