Plot Poles and Zeros

sysplot.plot_poles_zeros() draws poles as x markers and zeros as hollow circles o on the complex plane. Multiple calls to the function automatically cycle through colors and linestyles, making it easy to overlay several systems on the same axes.

import matplotlib.pyplot as plt
import control as ctrl
import sysplot as ssp

ssp.apply_config()

# First system: underdamped second-order
system1 = ctrl.tf([1, 1], [1, 1, 2])
poles1 = ctrl.poles(system1)
zeros1 = ctrl.zeros(system1)

# Second system: third-order with distinct poles
system2 = ctrl.tf([1, -2], [1, 3, 1])
poles2 = ctrl.poles(system2)
zerors2 = ctrl.zeros(system2)

# third system: second-order with repeated poles at the origin
system3 = ctrl.tf([1, 5], [1, 0, 0])
poles3 = ctrl.poles(system3)
zerors3 = ctrl.zeros(system3)

fig, ax = plt.subplots(figsize=ssp.get_figsize())

ssp.plot_poles_zeros(poles=poles1, zeros=zeros1, label="System 1", ax=ax)
ssp.plot_poles_zeros(poles=poles2, zeros=zerors2, label="System 2", ax=ax)
ssp.plot_poles_zeros(poles=poles3, zeros=zerors3, label="System 3", ax=ax)

ax.set(title="Pole-zero map", xlabel=r"Re[$s$]", ylabel=r"Im[$s$]")
ax.legend()
plt.show()